Measuring the Size of a Developer's Community?

Travelr9 asks: "I am engaged in a project where upper management is deciding whether to use Linux or Palm OS on a new device. Leaving aside the technical merits of each [in the context of this decision, either could work well] a key question is the size of the developer communities (for both OS and applications) of Linux vs. Palm. I have searched for info on this topic, and have come up blank aside from vague assertions. Is anyone capturing real numbers and stats? This also brings up an interesting conceptual question -- how do you measure the size, quality, impact, etc., of a developer community? Number of bodies isn't enough. Number of apps? Number of lines of code? Frequency of major releases in core application or platform categories? Can you measure a concept like 'quality of developer community' usefully?"