well, they *aren't* complaining. they're just enforcing the rules of this community, which is part of their duty as members of it. we don't mean any harm as long as your willing to cooperate.
i'm with Dazz in that ripping from fan games/rom hacks is one of those grey areas of sprite-ripping - it is probably best to either contact the original creators and ask permission to rip/use their sprites (which you appear to be doing now, so good). these sorts of community projects are more precious to the producers than say, a budget production of a video game to be sent out to the game industry for profit.
i'm with Dazz in that ripping from fan games/rom hacks is one of those grey areas of sprite-ripping - it is probably best to either contact the original creators and ask permission to rip/use their sprites (which you appear to be doing now, so good). these sorts of community projects are more precious to the producers than say, a budget production of a video game to be sent out to the game industry for profit.