In this case, it is a he-knows-better-than-us thing. He knew better than us (and the C::A people) what job he needed to accomplish, he looked at C::A, decided that it didn't do precisely what he wanted, looked at the code, decided that it would take too much work to make it do what he wanted, so he wrote his own because he had to get the job done
, which is ultimately the controlling factor here. If this was just an open-source, on-the-side project, I might agree with you more, but I think we can all agree that merlyn being able to afford food is a Good Thing.
You think that having numerous wheels is bad for open source? Would open source be better off if Linus Torvalds had decided to work on HURD or BSD rather than writing Linux? Having multiple wheels is a good thing, if only because you can take a look at what was good about the old wheels and build them into your new one.