I find it a bit irritating that the idea that a Fischer game without a cap might take a lot longer still seems to exist.
It doesn’t work that way. If I now play a 20/10 game with 60 min cap, the cap is irrelevant, as it will never ever be reached. If I play a 60/20 game, however, the site forces me to have a 60 min cap as well, and if I keep playing at a 20 s/move pace, it will punish me on average every other move. This doesn’t make sense, and it certainly doesn’t make the game faster.
If you want a faster game, use shorter time controls. If you fear that people might not realize the duration of the game, display it to them. You can calculate a rough upper bound very easily with Fischer time: for XX/YY (where XX is the basic time in minutes and YY the bonus time in seconds), the time for 300 moves in minutes is 2×XX + 5×YY. For example, a 20/10 game takes at most around 90 min =1:30 h. A cap only disturbs that calculation.
I’ll look into github.