Quote - What would you say: Am I allowed to do some poses for Antonia (!) from the sets and re-distribute them (with credit, of course!!) or not?

He says you can improve (modify) them, and he says you can redistribute them. So yes, the way I read it, it's OK to modify and redistribute them, providing they remain a free.

I think Schlabber's intention is clear, he does not mind what you do with the poses so long as you are not charging for something that he intended to remain free.