> We would like to thank GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years.

Is GitHub sponsoring Haskell development? Or is this them providing some free services (e.g. more Runners) because it's a large and importans OSS project?

GHC is hosted on Gitlab, the Github repo is just a mirror. So money.

https://github.com/ghc/ghc https://gitlab.haskell.org/ghc/ghc

Don't forget that SPJ had been working for MS for quite some years.