Underlying implementation already is. You can connect to iMessage and send and receive messages using the python implementation on your PC if you want.

Here is their POC in Python:https://github.com/JJTech0130/pypush

And their article explaining it: https://blog.beeper.com/p/how-beeper-mini-works

I mean, it won't be. It's quite clear that while the Beeper company may have good intentions on paper, they also definitely want to make as much money as possible. They aren't 100% bad, but also not 100% good either.

Considering they directly communicate with Apples servers and make money from that, I can't believe that their company will last long legally. The only way to keep Android users being able to use this will be to make it open source and go "underground". But I hope Apple will have a massive PR disaster on their hands while this happens.