I just have to give a shout-out to https://www.retrospect.com/ for anyone who needs commercial-grade backup software.

I've seen people call them "the gold standard" for classic Mac OS and, in 2024, when I asked about the possibility of licensing an ancient version for lack of something like rsync on my Mac OS 9 retro-hobby PCs, they let me use a download and license key that they keep around for when customers need to recover old backups on "but we can't provide support" terms.