The Buffalo Creek Software website is down and the downloads on its Wayback Machine site are not working so I created the following:
https://x-bit.org/spitfire/
On the site above I also created a HOWTO get SF working via telnet using NetSerial ($). Note, that Digital Man from Synchronet is currently working on opensource Virtual Modem software that I've yet to test:
https://web.synchro.net/?page=001-forum.ssjs&sub=syncanno&thread=144
--- SBBSecho 3.14-Win32
* Origin: The X-Bit BBS - x-bit.org - Forest Grove, Or (1:105/44)