Indeed, at first glance its source files seem to be free/libre because of the license you mentioned (I didn't check the dependencies, but I will relax my arguing just for the purpose of the final thought, and so I'll assume that the dependencies are also free/libre).
Point in case: source files and licensing seems OK. However, those termos of service about "having to make the new server not connect to the existing one" is somewhat interesting... It seems that they want to hold your data back with them, and not give it to you, so that they can figure "something" out. As a suggestion: I propose that over time, we contribute to GNU Ring, and re-test it with our families. For example, I'm giving a "boost" to them by trying to package it to GNU Guix, so more testers can appear, even if they have, say, some outdated things in their current operating system.
