Just based on this blog post it seems like he wanted the project to be more “professional” in some way that the rest of the developer group didn’t. I wonder if that difference in vision, combined with a (probably justified based on your comment) feeling that he was doing a disproportionate amount of the work lead to an unsustainable situation.

Calling it a post-mortem while others are continuing the project still seems kind of petty, though.

Software history is rife with projects that outlive a person like that leaving, though. Ulrich Drepper comes to mind immediately. They don't own the project.

Nope, he was not, and his software will be replaced.