Pippin Barr (previously) writes, "I have a history of making variations on existing games (see also: PONGS, BREAKSOUT, SNAKISMS), and Chesses (source, CC BY-NC) is a continuation of that. I find chess a really interesting game to play around with because it's so classic and sort of monolithic – it's fun to mess with tradition. Other than kind of formal enjoyment involved, I suspect the variations might level the playing field a bit and allow non-experts (or even non-players?) to play some chess."
I went through a larger set of ideas for chess variants that might be interesting specifically played via a computer (rather than just playing on a chess board), and of course culled some (fare thee well, Mirror Chess, Swaps Chess, and Pawn Chess). Mostly I tried to end up with a set that I think are genuinely somewhat interesting to play – both just to try to understand how to do anything sensible, and then beyond that to try to play "well" in the new version.
Chesses is also another data-point in the ultra-detailed process documentation approach called MDMA. So, if you want to, you can read a lot about the game's development by reading its process documentation, by going through its commit history, and by reading the research questions.