> This I disagree with. Why else would they made it available for download? (They might not be marketing the software, but they are marketing something -- e.g., their coding skills.)

Speaking as someone who has developed and released open source software, I can tell you why: because it's damn cool when other people find your code useful. An added bonus is that they sometimes send patches. I'm certainly not getting rich from it (in the form of job offers or other things).

Plug: I'm a committer on a tiling WM written in python which is also gearing up for release soon: http://qtile.org