Interview With BitKeeper Author Larry McVoy

Jeremy Andrews writes "KernelTrap has spoken with Larry McVoy, BitMover founder and primary BitKeeper author. BitKeeper, a distributed source control system, has been adopted by Linux kernel creator Linus Torvalds and condemned by free software icon Richard Stallman. In this interview, Larry looks back through the years, describing his exposure to computers and Linux. He also discusses the history of BitKeeper, from writing NSElite for Sun (which turned into their still used SCM, Teamware), to his desire to keep Linus from burning out, to the present day solution. The choice to not license BitKeeper under the GPL is also explained. Larry discusses much beyond Bitkeeper as well, exploring some of his other interests. Find the full interview on KernelTrap."

Comments

Congratulations to Linus

[WzDD]

For years, I've been skeptical of the Linux kernel development model, and specifically the its lack of source control. While it seemed to be "working", Linus has showed the strain several times on the kernel list. As far as I'm concerned, I'm glad he's found a tool that works for him - I totally agree with Linus' attitude of "use the tool that works for you, not its ideologically better, but otherwise inferior competition".

Hopefully this will at least alleviate some of the "Linus doesn't scale" criticisms, too.

free... as in freedom?

[TechnoVooDooDaddy]

Stallman can't get over the fact that Bitkeeper is NOT licensed under the GPL, and that Linus chooses to use it anyway. Presumably Linus just likes it better, and he's free to do as he sees fit. Freedom, that's an interesting word, because the mere notion of it means it must apply equally and unilaterally to everyone, or it doesn't exist. Stallman has repeatedly tried to exert pressure on people including McVoy to license things under *his* GPL, and complaining loudly when it doesn't happen. In other words Stallman is making an effort to limit their freedom with their own product.

Freedom applies to everyone, or it applies to no one.

The only part of the interview that matters....

[mshiltonj]

This is his response to the GPL issue. It's a good point. The choice is: Enough money to feed the family and pay the mortgage, or give back to the community and make a fraction of what you could have otherwise. It's not always this black and white, but many times it is.

Larry McVoy: I've never bought into the open source model as a self sustaining model for all software. It works in some places the software is tied to some other source of revenue, such as hardware, but in general, it stinks as a business model. It's fantastic if your goal is to have a lot of free software out there, but it starts to fall apart when building that free software costs more than you can extract from it in revenue.

BitKeeper is in that camp. There is about 25 man years of effort in BitKeeper so far, with no end in sight. We pay Bay Area salaries, so our cost for an engineer is about $160K/year. That's at least 4 million dollars no matter how you look at it, and that's a lower bound. I took a hard look at the Cyclic people who tried to make a business out of supporting CVS and they pulled in $145K in their best year. It would take 27 years to make $4 million at that rate, and that assumes we stop drawing salaries today. In this product space, if people can use it for free, they will. People have tried to argue with me that BitKeeper is a better tool and it would generate more support revenue. That's nonsense, exactly because it is a better tool. At least with CVS, there are enough broken or missing features that you could generate revenue to fix them. Maybe.

So I took a hard look at the situation and decided that I wanted to maximize value to everyone. I divided the world up into 3 camps: the free users, the commercial users, and the vendor. The goals were to provide maximum value to everyone and have everyone provide value back in return. Here's how it works:

Free users: these users don't pay in money, but they do pay. They pay by using the product and pointing out bugs. BitKeeper is a dramatically better product because of the free users. The BKL, the free usage license, insists that you are running the latest images, because that's where the free users provide value. It doesn't help anyone to get bug reports on problems we've already fixed. The job of the free users is to help debug the latest.

Commercial users: these users pay in money which funds further development. As a commercial user, they can pick which release they want to run, which sometimes means they stay back for stability reasons, perceived or otherwise. They benefit from the free users running a new release first, and it's typical that they wait for the timestamps in the download area to be a few weeks old before upgrading.

Vendor: we provide value in the form of the product and support. We get the bug fix value from the free users and financial benefit from the commercial users. The money is turned right around into additional development.

While BitKeeper is hardly a get rich quick scheme, it is self supporting. We've taken no outside investment, the company is built on the backs and wallets of the people who work here, and that's cool. It means there is no outside board of directors in the form of VC's telling us to stop wasting time giving it away. I know that giving it away has helped make it a better product, which is good for everyone, but I'd hate to be in the position of having to justify that decision to a VC before the fact. It's easy to see that things worked after the fact, it's much harder to see that they will work ahead of time.

The bottom line on the licensing scheme is that it was designed to give as much and get as much as possible to and from all parties. Licenses such as the GPL give more to the free users, but give dramatically less to both the original author and to the commercial users. Using GPLed software for everything is like living in a world where the answer for when you have an illness is "here are the plans for the hospital, you can finish building it and check yourself in. Oh, and here's the medical instruments you'll need, you can slice yourself open and poke around. You can do it, good luck!".

Licensed software is more like the insurance model. Nobody pays what it cost to develop the software, that's way to expensive. So everyone pays a little bit and the cost load is spread out. Yeah, for consumer applications like what Microsoft ships, they can get very rich because there is a very large market. But for applications like BitKeeper, it's a tiny market, about a million seats world wide, and there are about 300 different SCM tools out there. Hardly the area to go try and do a free product and hope that support revenue will work. It's just not realistic. There is absolutely no chance that BitKeeper would be anywhere near as good as it is today if we had chosen to GPL it.

Pragmatism

[jdh28]

Linus' approach to BitKeeper (and to everything it seems) is a purely pragmatic one. He has said that if there is a GPL'ed SCM that is at least as good as BitKeeper then he will switch. Until that happens he refuses to let idealism stand in the way of progress.

I think the BitKeeper license is an interesting innovation. My only problem with it, is that if I am using it for free, I am _forced_ to upgrade when new versions become available. Even on an open source project I wouldn't want to be changing something as fundamental as my SCM very regularly. If it aint broke and all that.

john

Re:Pragmatism

[Mr_Silver]

My only problem with it, is that if I am using it for free, I am _forced_ to upgrade when new versions become available.

So pay up and quit whining about it.

You're getting something for free, nothing, nada, zip that someone else has spent time and effort on, why are people not appreciative of this fact any more?

You don't go whinging about a free beer your mate gives you do you? And yes, even that beer will come with conditions (like you're supposed to drink it with him).

RMS condemning non-free, not BitKeeper itself

[Seth Finkelstein]

Agree or disagree, I believe the phrase BitKeeper ... condemned by free software icon Richard Stallman mis-states the issue. It's not the merits of BitKeeper _per se_ which are at issue. Rather, it is the very idea of the use of it - even if it's technically better!

What RMS actually said was:

Bitkeeper issue
The use of Bitkeeper for the Linux sources has a grave effect on the free software community, because anyone who wants to closely track patches to Linux can only do it by installing that non-free program. There must be dozens or even hundreds of kernel hackers who have done this. Most of them are gradually convincing themselves that it is ok to use non-free software, in order to avoid a sense of cognitive dissonance about the presence of Bitkeeper on their machines. What can be done about this? ...

Linux, the kernel, is often thought of as the flagship of free software, yet its current version is partially non-free. How did this happen? This problem, like the decision to use Bitkeeper, reflects the attitude of the original developer of Linux, a person who thinks that "technically better" is more important than freedom.

Value your freedom, or you will lose it, teaches history. "Don't bother us with politics," respond those who don't want to learn.

That's a very profound statement. It's easy to sneer at it, to dismiss it ad hominem. But he raises important points which deserve to be addressed in depth.

Sig: What Happened To The Censorware Project (censorware.org)

Ah, there's the rub

[Nygard]

The system is no longer GNU + Linux kernel. If it's about giving credit in proportional amounts, then X, perl, Berkeley, Apache, Netscape, and many other major contributors should also be recognized.

I do understand that some of these can be stripped away without impairing the OS, but some of them cannot.

While calling the whole ball of wax "Linux" may be overstating the importance of the kernel, calling it GNU/Linux understates the importances of all the other contributions.

Show me the money

[nagora]

Someone has come up with a way of earning a living under the following circumstances:

1. A lone programmer has a written a new program. Lets say it's an industrial level Cad system for Linux based on 20 years experience as an architect.
2. S/he releases it under the GPL but also writes a nice thick manual which is available as a PDF (let's assume s/he can't afford a minimal print run for this) to go with it.
3. The program works and works well and the manual is good enough to actually use the program; support is not a major issue.
4. The programmer continues on development of the program into new versions which are also GPL'd.

How does this programmer buy food to eat?

This is the flaw in the Free-Software model that McVoy is getting at. If you are a programmer who releases quality work which is distributed for free, how the hell do you survive?

The fact that the GPL does not prevent trying to sell software does not change the reality of distribution of such software in the Internet age.

I don't want to hear solutions based on using the software; the model here is someone who wants to be a programmer, not to remain an architect.

I believe in Free Software; I just can't see how I could ever be involved beyond it being a hobby funded by my real job.

TWW

What about FSF machines' BIOS & firmware?

[dstone]

In reference to the FSF, RMS says:
We have no non-free systems or applications on them now, and our principles say we must keep it that way.

So is this to say that their motherboard BIOS and all supporting microcontroller code, EPROMs, firmware and controller code in their video cards, ethernet cards, etc. all comes with source code?! Impressive. Where do they shop?

Re:Role models

[JordanH]

• Good. I like a role model who has the sense to use the best tool for the job, and who doesn't waste his time with inferior tools.

Best has a context associated with it. RMS believes that best is always free as in GPL'd. Anything else, to him, is inferior.

Linus himself was quoted as saying "Making Linux GPL'd was definitely the best thing I ever did. "

I'm concerned about what I see as extreme pragmatism on Linus' part. Surely, better software, in terms of features and useability, isn't the only criteria for determining it's selection. Price is obviously a major criterion with such internet-developed projects as the Linux Kernel.

As far as I can tell, the BitKeeper license doesn't insure that future versions, perhaps even versions necessary to run on future OS releases, will still be free of charge and without source, we can't be sure that we could make it work on those releases.

Maybe this is just paranoia and there's really nothing to worry about, or maybe not.

RMS is insistent and consistent. Somebody has to be.

I like Barry Goldwater's statement "I would remind you that extremism in the defense of liberty is no vice." To RMS this is about liberty and he doesn't compromise.

It seems to me that there are two choices: The GPL is adopted for purely pragmatic reasons because we can outcompete closed source development. The other is that the GPL is adopted as a principled position.

If we take the first position, then will we stop using Linux the moment something better comes along in terms of features, useability and stability? After all, the existence of BitKeeper proves that, at least in some contexts, that closed source development is superior to Open Source Development models. Doesn't it?

Let me ask you. Should we adopt MicroSoft software if it offers better features and useability? Or... are there other concerns than the narrow "best tool for the job" consideration?