If he's just planning on making some "mini-hacks" (similar to the ones in the first post) to add more functionability to the hack, then
technically I don't think he would need permission... And either way I wouldn't mind.

If he's planning on making some other hacks that are
based on mYvBindex and it's code, but are not the same hack, then yes, you're right and he would need my permission first.