[gonzoua]

Less companies contribute to FreeBSD because its market share is lower than the one of Linux. And I believe first part of Beno's answer is correct - it's because FreeBSD version of RedHat didn't happened at the right moment. RedHat was there when window of opportunity opened for open source OS and was able to boost linux ecosystem by paying Linux developers which led to higher adoption which led to more contributions from corporate world.

GPL does not require contributions. GPL requires access to sources. Not to changes history, only sources. Contributions happen because it's more profitable for company (in long run) to participate in community and influence development than to be a passive actor.

My point is: license has very little to do with market share in this case. It's more about being good enough and having certain amount of luck when the right moment arives.