GPL's Strength
Morty writes "So, why hasn't the GPL been successfully
challenged yet? In this article, Eben Moglen, General Counsel to the FSF, explains that the GPL is in a stronger legal position than most licenses. Most licenses restrict the user from doing what would otherwise be legal. Because the GPL (and presumably, other free/open software licenses) let the user do things that are otherwise illegal (copy and redistribute software), the GPL is in a stronger position to dictate terms. If the user doesn't accept the terms of the GPL, the default is for copying and redistribution to be forbidden under copyright law. I had never looked at it that way before. . ."
This is Moglen's follow-up article referenced in the first one.
The GPL does not restrict or regulate the use of software at all. The only activity the GPL restricts is the conditions under which covered software can be redistributed.
You quoted, "let the user do things that are otherwise illegal (copy and redistribute software)". Most Open Source licenses don't regulate that activity either. The other activity that is regulated is preservation of the original copyright notice: you can't claim someone else's work as your own. The BSD, Apache, X style licenses say you can't plagiarize but can do anything else you want
You are correct, though, Microsoft's EULAs do restrict use of the software as well as copying, redistribution, reverse engineering and reselling.
The point Professor Moglen was trying to make is that in legal terms the GPL is SIMPLER than such a EULA and is therefore less prone to failure. I would imagine that is largely true of most other Open Source licenses.*
* The MPL/NPL, APSL, IBM's public license and other corporate style Open Source licenses tend to be complicated and fail the simplicity criterion.