Open Source is one person

The ones that come to mind are

- Hans Reiser, maintainer of ReiserFS. I think very few people use ReiserFS these days.

- Ian Murdock, creator of the Debian distribution. Debian lives on, but the project was also set up specifically to distribute maintenance.

- Jim Weirich, creator of the Rake build tool. I'm not a Rubyist so I don't know how it was affected, but I assume it's such a big part of Ruby other people took over.

- Peter Hintjens, co-creator of ZeroMQ. From what I understand, Hintjens was never the main developer but an active promoter. The project lives on as far as I know.

- Terry Davis, creator of TempleOS. I think development on TempleOS stopped.

IMO, it has a lot to do with usage and the availability of alternatives. With ReiserFS, there were a lot of alternatives, both available at the time or announced shortly. While ReiserFS pioneered a lot of ideas, many of them showed up in alternatives fairly quickly. TempleOS is had a pretty limited user base.

I’ve seen many projects in the Clojure ecosystem get picked up and maintained by other folks. The key was always that the projects had an established user base of some notable size and something distinctive about them that made switching to other alternatives less desirable than continuing to push forward with a new and possibly more mundane maintainer and feature schedule. I’ve also seen a lot of “abandonware.”

So, it’s a bit of a mixed bag.

Reiserfs died because alternatives, like ext3/ext4 and btrfs, became readily available.

TempleOS has a fork called ZealOS. Terry Davis really was the "Wesley Willis of programming", and he had friends and fans worldwide, some of whom have taken up TempleOS development under the ZealOS banner.