I think Matt Mullenweg has every right to take the action he's taking. It really seems like many companies are perfectly happy to exploit open source products.
In this case, it seems like one company makes a lot of money using the Wordpress codebase and doesn't want to make equal contributions. Then they use the money they're making to turn around and sue Wordpress for standing up for themselves.
If I were Matt Mullenweg, you can bet I would be incensed! I'm honestly very surprised that Matt Mullenweg is facing such criticism when he's simply trying to protect IP that he and the community have spent a lot of time and money building together. It's only natural to want to ban the freeloaders, and in any case, it's a little outrageous to think anyone is entitled to access to the resources and creations of others with or without compensation.