(Posting on behalf of the @SGB)
There has been a “sponsor” button on the
stan-dev/stan repo for a while now, but as of today GitHub has approved the
stan-dev organization for participating in the GitHub sponsors program.
There’s now a “sponsor” button at the top right of the main
stan-dev organization page on GitHub and also one for each of the individual repositories. Any funds that come in through the GitHub sponsors program will go through NumFOCUS.
Currently this is just a way for people to donate to Stan because we haven’t set up any “rewards”. GitHub will let us offer rewards for different sponsorship tiers, so if anyone has any ideas for what we could offer or wants to volunteer to work on that please let us know!