Here's something cool and nostalgic.
Working with Microsoft, and getting the company's approval, the Computer History Museum today has released the source code for the 1982 release of MS-DOS and the 1990 version of Word for Windows.
Making the bits available as downloads, the Computer History Museum has also wrapped a nice history for each product around each release and download link.
Unfortunately, as soon as the release was announced, the Computer History Museum web site started experience a multitude of outages. I guess the site must not be utilizing a modern Cloud hosting provider. So, good luck getting the pages to load. If you are able to view the pages, here's a tip -- don't refresh the page.
I'm not sure, exactly, what one might do with the source code for these old applications, but who knows, maybe a whole HAM Radio/Amiga computer community will grow from it.
You can read all about each release and download the source code bits from these links:
The Computer History Museum, a nonprofit organization, is based in Mountain View, California.