TMG is without a doubt something that needs to continue. I think that we all agree with that. For whatever reason(s) Bob cannot keep it going and to be honest for one guy to maintain a piece of software as good as TMG for 25+ years is phenomenal.
At the same time there are many many things that people have asked about over the years: can it do this; can it do that; can you add this; can you add that...
So what if as a community we take on Bob's legacy? What if we were to ask Bob to make it open source under a GNU licence?
I don't know if Bob would be up to doing something like that but it seems to be at least something that we as a community could talk about.