Legality has absolutely nothing to do with it. Having to support phones with unofficial firmware would be a customer service nightmare (their reps hardly know anything about how to use the phones as they are), not to mention the possibility of bricking your phone through a bad flash. This is why it voids your warranty, and is against the TOS of this site to discuss it. Same thing with swearing and personal attacks against others, not illegal, but against the TOS of the site.