And I reason that if this really is an open source (though unofficial) product then it probably isn't using the GCE functionality for Text-to-Speech. ( https://cloud.google.com/text-to-speech/ )
The code uses Firebase (etc) though.
Can anyone confirm? If the engine is any good it'd be good to know that it isn't hard tied to any specific cloud vendor ...
Otherwise I've just tried MaryTTS (which worked really nice).
Can you recommend any other good Free, OSS solutions? eSpeak really sounded terrible, IMO. ( http://espeak.sourceforge.net/samples/raven.ogg )