We can't grant users a license to waive copyright.
Yeah I know, that's why I said "essentially". Probably better to say "effectively". You cannot waive copyright, but you can require publishers to grant users a license with almost the same rights as copyright. Specifically, "license to distribute" sounds like it officially allows unlimited copying or pirating. I'm not sure I understand this right, I'm not a lawyer, I just saw it in terms and raised a question :)
As for content scraping, do we need to make rules about it now?
Ah, no, I don't really need rules. I guess being reasonable is enough. Although I would appreciate at least some informal guidance, i.e. what is recommended request rate for itch.io, or whether it's OK to download the games themselves. Downloading and analyzing terabytes of data is not that costly nowadays, especially considering that incoming traffic on clouds is usually free, but obviously some cost will be on itch.io for its outgoing traffic and CDN charges.
To be clear, I'm not working on this project right now, and it's not that serious. What's implemented (quite a while ago) is this: https://itchy.quyse.io/ - simple analyzer of publicly available itch.io projects. Example analysis (game I'm working on): https://itchy.quyse.io/game/19957. The idea is to expand analysis to all itch.io projects (rather than do it on-demand), and gather statistics about games binaries/resources, like what percentage of all games uses Unity, or what are the minimal required Linux distributions for games with Linux version, etc. I hope I'll get to work on it as a weekend project at some point.