[turol]

Strange that they list FreeDOS, DR-DOS and MS-DOS as separate OSes even though they are very similar. They are effectively ABI-compatible, unlike the different Unix flavors.

[pjmlp]

Almost, as everyone knows DR-DOS, MS-DOS and PC-DOS were like 99% compatible, the problem was when one was lucky enough to trip on that 1%, because they reverse engineered MS-DOS (even the IBM's PC-DOS license did not provide access to everything Microsoft was doing on MS-DOS).

[_joel]

1% like running Windows 3.1? :)

[coldacid]

Considering that DR-DOS is a linear descendant of CP/M with MS/PC-DOS ABI compatibility, it's certainly a separate OS. Same for FreeDOS. There's enough difference "under the hood" for each of them, however.

[mattl]

They list OPENSTEP and NeXTSTEP as separate OSes too...

[pjmlp]

And they were, NeXTSTEP did not run on Sun workstations.

That would be like saying NextSTEP and OS X were the same as well.