Software licenses aren't enforced by magic but they are social contracts: even if nobody has the resources to go after you for doing it, it is pretty clearly against the permissive licenses' spirit to misrepresent yourself as the author
It's also pretty clear that the real author gave you permission to misrepresent yourself as the author, as long as you retain the copyright notice. If he didn't want you to do that, he shouldn't have given you permission.
It's also pretty clear that the real author gave you permission to misrepresent yourself as the author, as long as you retain the copyright notice. If he didn't want you to do that, he shouldn't have given you permission.