You also get the satisfaction of knowing that you really have covered every aspect, since you can see by inspection how it fits together. I discovered quite a lot that way. I think the term 'open source movement' is a little misleading. Open source as a concept has been around a long time, longer than commercial software in fact, and it will always continue to exist in one form or another. So I don't think open source is in any danger.
Individual projects are another matter.
As a project becomes high profile and attracts commercial interest, it starts to blur a little at the edges as it finds its own particular balance between open and commercial interests. Linux and FreeBSD demonstrate two alternative approaches to the same problem, based around their own particular licensing and project ethics. Since all of them are demonstrably succeeding, both as projects and also in terms of defining what their principles are, I think the 'open source movement' is doing very well. Although I've experimented with both PHP and Java, I've never felt sufficiently motivated to use either in a serious application - yet. Something I'd noticed but never quite articulated until I came to write Professional Apache, is that there is not as great a difference between the various web technologies as people tend to think.