Excelsior! BBS is entirely free and very CNet like, tbh. Runs fine on a XP/UAE box I have. Can be DL'ed at:
http://www.excelsiorbbs.com/downloads.htmlOne of the devs/caretakers of E! is also here on A.org too - LamboJay, and is a tremendous help, super nice fellow to boot.
I've run Zeus and DLG mainly lately, but Zeus handles my PPC SAM 440 better than DLG so I've mainly stuck with Zeus. It's not free (Zeus), but only like $30 or something to buy and it's a great piece of software that is still maintained to some degree.
DLG is now open source, including the source code. DLG BB/OS isn't as pretty and intuitive as the more GUI BBS like Zeus and E! are from the sysops end, but it's absolutely rock solid and blazing fast esp. if you plan on having usenet or FTN's. DLG can be found on Aminet, including the source - and works well in an emulated environment. It's entirely modular and likely the fastest, most stable BBS software I ever ran back in the day in combo with GMS Mailer and MailManager.
I would recommend taking a peek at Zeus first, tbh - it really is a nice BBS program and can be setup in all sorts of ways, the GUI on it is just great and virtually everything is just Arexx based. Likely the best Amiga BBS prog out there if you enjoy a real customized setup for your users. I was a beta tester for Zeus back in the day and it's still every bit as good as it was back in the 90's.
http://www.zeusdev.co.uk/As for CNet, much like everyone else I've been trying to get ahold of it for what seems like years now, as I was a 3.x regged user of it, but had zero luck.
Good luck!