dos211
just the MS-DOS 2.11 sources, I re-aranged stuff and made it (slightly) easier to rebuild on Windows.
Other than wanting to build DOS from source, I guess it's not all that interesting.
But it was to me.
You'll need the excellent msdos player http://takeda-toshiya.my.coocan.jp/msdos/ to bulid natively on Win64.
It's MS-DOS 2.11 so unless you really like XT's you'll probably be disappointed.