Yes, some corporate users contribute financially back to the project, and we're thankful. But why should we have to be thankful? The GPL already provides a tried and proven legal framework for requiring downstream users to publish their improvements for others to use. Free software is an ecosystem where everyone helps and everyone benefits. When the BSD license allows parasites like Sony to benefit to the tune of billions of dollars without giving a line of code (or a penny) back, that breaks the ecosystem.
I'm calling Sony out particularly because they are not included in the list of corporate sponsors in the article. The Sony games division made $3.2 billion in revenue in quarter 1 2016, this is unacceptable.