I always liked C-net on the C-64 and I know some programs were converted over. Was C-Net BBS one of them? And has it been revisied for telnet?
I went through thinking about setting up a BBS again a while back, so my news is current as of about 10 months ago.
CNet Amiga hasn't seen a new revision in a long time (since the late 90's). The newest is CNet Amiga 5 Pro. Though from a user standpoint, it doesn't look much different from the old CNet 2.6 I used to run in the early 90's. I hear it has some nicer SysOp features, though. The CNet Amiga 5 can run off telnetd.device to be telnet-aware. Possibly older versions can run off this device, as well. I haven't actually tried my 2.6 on it, since the only working copy I have installed anywhere is on an unexpanded A1200 that doesn't have TCP/IP installed.
Now, the bad news is that CNet Amiga seems to be caught up in a dispute, or something. It's still commercially copyright protected, so you can't just download a full version. You may be able to purchase a full version and keyfile from the author(s), if you can find them. HMetal on here may be able to give more information, as he was an owner of the rights to CNet at one time.
Some other Amiga BBS, including DLG, have been released free with source, so you might want to look into some of those, as in this day in age, you are going to be your own support. ;-)