I think it's similar to adding a note to a book, and then removing that note, leaving you with a the original book. That scenario doesn't violate copyright law as far as I'm aware.
That's not how patching a rom works. You directly replace data and the formats that let you undo have to put a copy of the original data in the patch file. So yes it is a risk.
That's not how patching a rom works. You directly replace data and the formats that let you undo have to put a copy of the original data in the patch file. So yes it is a risk.