Yes! I was racking my brain trying to remember what it was called. Back in the early 2000s I ran BeOS on my desktop and absolutely loved it. Then when they went under, I followed the effort to come up with an open source version with guest interest. There was one effort that wanted to build everything from scratch. That's what was later renamed into Haiku (I think initially openBeOS maybe?). There was also BlueEyedOS who thought you could get there faster by building on Linux and X11.

I think Haiku got more traction because at the time people felt that it should run BeOS software without recompiling. I have long wondered what would have happened if BlueEyedOS would have gotten most of the effort.