Cups has been forked after Apple supplied only one commit in all of 2020

CUPS was almost entirely[1] made by Michael R Sweet who left Apple close to a year ago[2] and now works for his own company.

Completely understandable to move the upstream repo away from Apple, I don't think there's much else to it. He's been very active in the fork AFAICT.

His Sponsors page: https://github.com/sponsors/michaelrsweet

[1] https://github.com/apple/cups/graphs/contributors

[2] https://www.msweet.org/blog/2019-12-20-left-apple.html