Been using Slate as well but it's not maintained anymore. I wanted to switch to Phoenix - https://github.com/sdegutis/Phoenix/ which is from the same guy that this Hydra. I think the idea of Hydra was the rewrite it in Lua but I can't speak for him. Will definitely try it out asap!
Hydra is indeed my successor to Phoenix. Phoenix and Zephyros (and AppGrid if you can find it) are deprecated in favor of Hydra. But I can't just delete those projects, as existing users may not want to port their configs to Lua. Oh how I wish I could though.
I find it great that you've opted for Lua over JS. I see far too many projects with JS shoveled in where Lua would be a better, cleaner, and simpler fit.
I'm very glad to hear that. I was expecting a lot of people to be disappointed that it's not JS, but honestly I think Lua is a lot cleaner and simpler, and it is just so small and easy to integrate with in C, it's really hard not to use it in a project!
I'm one of those people still using Zephyros, mostly so that I could keep using beer (https://github.com/v-yarotsky/beer). I skipped Phoenix but might give Hydra a try (knowing no Lua though) just to see what you've been doing with it.
[0] https://github.com/jigish/slate