Developer and publisher Stardock's PC titles will now be available to Steam users, starting with Sins Of A Solar Empire: Trinity.
In May Stardock sold its own digital delivery service, Impulse, to GameStop.
"With the sale of our former PC digital download technology to GameStop earlier this year, we no longer have any conflicts of interest in offering our titles to other digital distribution channels," said CEO Brad Wardell.
"We are starting with Sins of a Solar Empire: Trinity with other titles being made available over the coming weeks."
Steam and, GameStop PC Downloads, will offer the game at a discounted rate this week.
The company has also promised more platform announcements in the coming weeks.
Stardock was founded in 1991, and as well as developing and publishing PC strategy titles, created Object Desktop, which allows PC users to modify Windows.