Earlier quoted context omitted.
Not only are you not allowed to distribute it by the license, actually distributing it would get you sued for patent violation. Using anything you find in the code will probably get you sued for patent violation, too. EDIT: I can just imagine a future lawsuit: A: Did you read the MS-DOS source code released by Microsoft on XX? We have logs to show you downloaded it. B: Yes, but that has nothing to do with this lawsui…
Don't patents only last 15-20 years?
P.S. Google Patents is useless for answering this question. "Referenced by" is included in the search, so any patent from 1983 that is ever referenced by a Microsoft patent (from any year) shows up in the results.