I think Samba was my first introduction to the idea that using a non-official/reverse-engineered implementation of something to piggyback into a closed ecosystem may not actually be preferable to either shunning that ecosystem entirely, or just buying into it. I loved it in concept, but in practice not so much.

Samba is a protocol, Microsoft doesn't have any costs associated with more users of it. GP is asking about APNS, which involves Apple servers and therefore costs Apple to handle more requests, however minimal per individual request/message