McBBS is a 16 bit application originally designed to work with DOS. MS/PC-DOS is no longer manufactured, and the last major modifications to McBBS were back in 2001. A slight update to the install package was executed in 2006 to accommodate a computer user group in the Ukraine that became the version now distributed over the internet since it is the only version that never needed the install floppy disks; it is the same very last McBBS version (v5.5 rev. 3) except for the modified install program. McBBS, DOS, DMCS Technologies and the computer language McBBS was written in are all extinct, making it unlikely any patches or new versions will come by anytime soon to help McBBS defend itself against the advancements of time and technology.
Although the new 64 bit computers still can execute 16 bit programs, operating systems like Windows (specifically 10) won't allow them. Why this functionality was removed by Microsoft is anyone's guess as there seems to be no computer science based reason for it, nonetheless it leaves legacy software as dead as dinosaurs to Win10 x64 users. Dead... unless they use third party applications that get around this limitation.
While the perfect solution is to run McBBS in a legacy PC running DOS (or a 100% compatible equivalent), many operators have found a good facsimile is to install and employ "DOSBOX" (https://www.dosbox.com/) on their computer. DOSBOX simulates the MS/PC-DOS environment of the past and allows many 16 bit DOS based applications to run in Windows 10 x64. Alternatively you could install Oracle's "Virtual Box (VM)" product (https://www.oracle.com/technetwork/server-storage/virtualbox/downloads/index.html) and then install a real version of DOS within it. While DOSBOX simulates DOS within the Windows environment, VM runs the real DOS and emulates any computer you want, including disk drives RAM, Processor, video, etc within the Windows environment. VM is a more perfect solution outside of a real legacy PC but it is far more memory and processor intensive than DOSBOX and, quite honestly, should not realistically be used with any machine containing <4GB RAM. Both products are free.
When configuring your "virtual box", whichever you choose, McBBS's needed environment is:
PS> Using McBBS with any version of Windows 95 or higher may involve using the so-called "Windows Override Switches" to access the modem (see manuals inside ZIP install archive) otherwise it works native within the "CMD" box.
Please note: McBBS has not been tested in a lab since Windows XP was ruling the PC world. We know it works on XP but it was never tested higher.
This information is based on information given by operators of the program, your results may vary. Untested! Use at own risk.