On the contrary, out of all the free OSes out there, it was Linux with GPL the most successful, because companies could contribute back knowing that their competitors would not take the code and run away and produce proprietary forks backed by large marketings budgets.

See FreeBSD and Mac OS. If I contribute to Darwin, Apple will take my changes to improve their product. I get nothing in return. This may be fine for an individual, but for a company who depends on a product, it's a bad scenario.