LWN.net founder and kernel contributor Jonathan Corbet offered an analysis of the code contributed to the Linux kernel between December 24 2008 and January 10 2010. 18% of contributions were made without a specific corporate affiliation, 7% weren't classified, and 75% were from people
working for specific companies in roles where developing that code was a major requirement. "75% of the code comes from people paid to do it," Corbet said.
via >
http://www.osnews.com/story/22786/75_of_...Developers
I suppose some could see this story as a reason to justify why open source 'doesn't work', but I don't think it matters why or who writes what code, as long as it is licensed so that all can benefit from it. I think the participation of businesses in this type of free development and the interaction between commercial software vendors and the traditional hobbyist open source/free software developers is overall a really positive thing.
Look at something like WebKit. OK, there were issues at the beginning with Apple not being very open about their development on the project, and it is somewhat disappointing that KHTML and WebKit are so disparate, but now you have developers from Apple, Google (who now compete on a lot of things), other companies and just hobbyists all making a really solid product. In that case, it is in everyone's interest to work together and write the best code possible, which I think seems to be working really well. The competition between different vendors of products which include WebKit happens at a different 'level', if you like.