Hi Paul,
Both have their proponents, and I believe both are free to use. (I know for a fact that BandLab is, but I've never used Kompoz.) I haven't used BandLab much myself, because its paradigm (hunt for collaborators, do a project, rinse, repeat) doesn't fit with my usual working method of networking with people I already know. I have been promising myself over and over that I am going to get back into it for a while, at least enough to be able to answer basic questions like yours... but my To Do list has gotten a bit out of hand, starting in, uh, 2006...?