Earlier quoted context omitted.
I agree - even if they're legally allowed to just take his work, it would've been nice to let OP know.
Considering they fully own all of the IP present in the OPs work, I would imagine they are within their full rights to just take it without asking. OP is lucky not to get a takedown notice and judging by his attitude he knows it. Good to see people playing nicely together :)
It’s basic courtesy (plus MIT license, if you prefer).