I did some work for Collabora for a few months. Those guys are amazing! If you want a commercial support contract for any of the software they develop, just do it. They do a fair price for corporates, believe in open source and thus I found my colleagues were super responsive to paying customers and took a great deal of pride in the quality of their work.

They also actively pushed out their code in usable format I to the main codebase. And they did it frequently. They also got access to documents for testing and performance testing others didn't have access to, so the stuff they pushed out actively helped the project, but because they had support contracts they were able to backport to versions the main developers wouldn't consider.