>>51009400It's legal, depending on whether or not ToS is legally binding. 4chan prohibits it, but I don't think they enforce it unless you're putting massive stress on the server. That rule's lumped into a VPN/Tor ban, but it can't be enforced in the same way.
>>51009997Archives actually have it really, really tough. The /g/ archive I use is pretty reliable and they've been able to stay up, but Foolz and anime.moe stopped because of the insane load caused on their servers by scraping and the amount of images stored.