Sounds similar to the China Dos Union MS-DOS "7.1" which used the DOS from Windows 98 and included FAT32 support, long file names and a CD-based installer.
(The rest of cn-dos.net is also worth checking out if you read Chinese or find Google Translate to be sufficient; this is an example of one of the forgotten-yet-very-interesting parts of the Internet.)
http://reboot.pro/uploads/monthly_04_2008/post-5-1208637282....
I'm not sure how they did it though, maybe when I have the time I'll look into it since this is a very unusual software.
(or maybe they binaries are actually pretty similar, so all it needed was a slight API change for file name lookup)
http://www.computerhistory.org/atchm/apple-ii-dos-source-cod...