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!