I don't think Patchou wants to spend more time working from scratch on a new Plus! for macs, and before he did that he'd have to learn macs' language anyway...It would probably drain his energy and his time working on the Windows version.
If you want to make a version of Plus! for macs, then go ahead, just don't call it "Messenger Plus!" and acknowledge Patchou for inspiring you to make it in the first place
/ 
