Yes and no. The original firmware / host driver stack was open (shared?) source called MyriAPI. It was so terrible that spawned an ecosystem of uni and research lab projects to implement replacements. I worked on one such project at Duke (Trapeze). Others included BIP, Fast Messages, Active Messages.

MyriAPI was later replaced by a new firmware / host stack called GM. I think at some point we stopped shipping firmware source. I think that point was the transition from MyriAPI to GM...