I just looked into it again out of curiosity. It no longer requires a Google login (nor does it even require Google Play services, because I don’t have them. This will probably change once they go paid, which they’ve apparently rolled back since the iMessage debacle).

It says it supports SMS/RCS, but it actually supports neither. All it does is connect to your Google messages web account. This is an absolute joke for an app that bills itself at the top of it’s home page as “all your chats in one app” and it doesn’t even support the most common chat method.

As far as I can tell the app is still closed source.