Given that the installation guide[1] says you need "A computer running OS X 10.10 Yosemite or higher (and a place for it to stay)" I'm pretty sure they are just relaying your messages through an actual desktop iMessage instance, so probably. I imagine a lot of Android users don't have a computer running MacOS to do this though, so while a cool solution, it probably doesn't help the majority of people.

1: https://airmessage.org/guide/