Is it free forever and ever and ever??
I went looking through their site, and I couldn't find where they specifically say that the program will remain free forever. But the implication is pretty strong - in their "About Us", they write:
BandLab’s mission is to break down the technical, geographic and creative barriers between creators, collaborators and community by providing a completely FREE and unlimited service.
Still, it would be nice if they were a bit more explicit about what will remain "free to download", and what is planned for "targeted for monitization."