A comment in this thread gave me a hint on how to possibly reproduce what happened to my friend's account.
Guess what, it worked, so here we go, the requested fraps video shot by myself, on youtube actually showing multiple "gold account required" screens. I even left the ingame sound in. Not that any of this will prevent people from screaming 'fake!', not that I care, but here you go guys.
Yes there are no non-foundry characters on that account. It was created literally a few minutes ago and I didn't bother with that. Plus I have to emphasize that the creation of this account had the only purpose of checking out my theory as to how my friend's account got "bugged"/converter, and to create this video myself, I did not and do not intend to take advantage of this.
Any more proof requests? Can't guarantee I will bother with them as well though.
note: after watching it on youtube I had to notice that the quality ended up being rather low, at least at this point youtube only offers 480p. Almost everything should be visible though. The exception is the very last part where the main login screen is shown. The red text there also reads "A gold account is required to (...)".
I have no intention of exploiting the situation, but I am not going to tell my friend to contact cryptic's billing so they can start to, well bill him, either.
Althought I should mention that once we started realizing something was wrong with his account, or let's say, not quite normal, he did state he might just buy and pay for the game anyway in the end.
While the shot certainly doesn't count as proof beyond question, I wouldn't be surprised if there were already a closed beta going on quietly. It would contrast completely with the openness with which CO's switchover was worked out, but that would match STO's pattern of contrasts with CO.
I remember fiddling with a trial account on a friend and something coming up where it referred to the account as Silver. This was before even Champions Online went F2P. (I think it was under the my account tab... no wait I remember, it had to do with trying to get on tribble iirc).
Even with the video, I'm still not convinced. Yes, I do not doubt that STO is going F2P, but this is still not proof that it is. Also, I thought that the demo accounts were suspended. How is your "friend" able to do this without a paying account?