It looks like there are not that many defunct roguelike projects written in C++ (or C). I've tried to find one browsing roguebasin, but no luck yet. I've also tried my luck with two projects, but I found out both of them were quite impossible to continue (first one was Abura Tan, I think the second one was Trollslayer). I like the idea of unfinished game which could be easier to develop than just starting from a new project.