I tried installing ReVanced recently. The configuration of the system (install a downloader/updater which then installs the app) was a huge turn-off. Why is it so complicated? Moreover, why not NewPipe or LibreTube?
So instead of "stolen software" they distribute "patches" and a patching framework.
Legally distinct and modding is a much grayer area.
It's code you run locally to company the file, change the bytecode and repack it.