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