I found out that B-17 Flying Fortress has been released as freeware:
Edit maybe not but xcom 1 might be...

http://www.dosgamesarchive.com/profile/microprose-software/

I like it how on that page there's a Tex Murphy ad straight to GOG :)

Haha, how does MicroProse get all the credit for Transport Tycoon? I'm pretty sure that was 100% Chris Sawyer. Perhaps he was working for MicroProse at that point.

http://www.mobygames.com/game/transport-tycoon

That's the way it works, you know. Whichever individuals worked on a game, it's the development studio that's listed as developer.

You know, I was browsing that site a couple days ago and saw that X-Com was free there. I'm thinking now, it must be a mistake.

Sometimes a publisher offers older games temporary as freeware to promote new games. Regarding mobygames Microprose did that for the newer B-17, see on Mobygames at the bottom under Trivia.

Edit: I can't remember that there was something for the first x-com game. With it's popularity I believe we would read something like that on more pages.

Betrayal at Krondor, B-17, Gateway and a number of other oldies had limited time freeware periods.

Well as I said, perhaps he was still working for MicroProse.
With RCT he's listed as the developer, so I can only imagine that he'd gone freelance or something.