Here's a link to the 2KGames page where the original Railroad Tycoon was released for free:

http://www.2kgames.com/railroads/downloads.html

Being the owner of the original Railroad Tycoon I feel I should let everyone know that despite the information Firaxis provided, the link you posted is for Railroad Tycoon Deluxe and not the original Railroad Tycoon. Despite it being a sequel to the original game and having many more maps on which to play, I still preferred the original (although that may have been because of the cheap, underpowered PC I was playing on at the time).

But thank for posting that link!