But, despite being copyrighted materials, if they didn't distribute them it amounts to fan art, which, as it doesn't make profit, would NOT be prosecutable against as it would be held within freedom of speech. This is the reason people who make skins for computer games of copyrighted characters can not be prosecuted, if it's not profiting and not costing the copyright holder any money(neither of which these texture hacks were), it is not a case of infringement(or, at least, not a case that would hold up in court). The reverse engineering may be a trickier issue, but if that was the issue then ALL the texture hack sites would have to be taken down to make a solid legal case(If you only care about one of many doing the same thing, it shows bias, which can cause large issues for the prosecution in legal proceedings). Also, if that were the case we come back to the bigger concern being ROMs and emulators, as they rip every bit of data from games AND distribute it.