Just a follow up on this. We have, unfortunately, decided to abandon use of GitHub for our courses other than specialty courses for those over 13 to introduce them to it and use it further. Before the terms re-clarification we had assumed a lighter position from GitHub on the whole under 13 thing (much like Google) such that parents could create accounts and share them with their children until they were old enough to have their own. The GitHub terms very clearly spell out that everyone gets two accounts maximum, one for regular use, one for 'bot' use. This effectively forbids parents from letting any of their children use their account.
In short, while we use GitHub a lot for our school IT code, we practically do not use it at all for students since the majority of our students are 9-13.
This decision was a very hard one. All our work on using GitHub classrooms with Workbook/Textbook approach has been abandoned and we have built our own system internally that uses nothing but the terminal and vi, which I ended up loving much more. Our students do zero context switching when doing their challenges, reading about them, and writing the code—even checking scoreboards and all remains entirely on the terminal. Only web students use their web browser. Turns out this use of ~/www for their web site is also much clearner for web courses, which had us training students how to use GitHub to create their site before. In all I am happy about the move overall and am glad this was clarified before we had implemented more of our Distributed LMS based on GitHub.
That said, we still really love GitHub.