I'm a CircleMUD lover by nature, but of course it lacks many of the tools I require.
I will confess that I'm a bit of a flake myself. I've started many MUDs in my life and gave up on them anywhere between 3months and 3 years, only to get 'the itch' again sometime in the future and then start up something new from scratch several years later.
The number of times I've patched up Circle3.1 is beyond count now, and I'm only going to do it once more.
So I made a very long list of patches/tools/annoyances/bugs/problems that I plan to fix one final time and actually archive it properly.
There are also some more deep things I'd like to change about the way things are handled in the game, such as the mail and board systems. But I do not intend to add more game specific details which will be more appropriate for my personal MUD which I will develop *after* this intermediate project.
There is no reason not to share.
What I'd like to know is, at what point is it appropriate to branch the code and call it something else other than just a "heavily modified CircleMUD"?
Please double check the question. You answered a different one.
Your question, as you asked it, is not going to yield a clear answer. It depends.
On the one hand, at no point is it appropriate for a derivative work not to credit the original.
On the other hand, assuming you do credit the original sources in the way their license requires you to, you can call your codebase anything you please, at any point. You are in the best position to decide that, not a jury of peers.
You've made a bunch of changes, so you've already "branched" the code.