Update: The offer expires on April 24 at 10am Pacific.

Developer Tripwire Interactive is giving Steam users a freebie. Red Orchestra 2: Heroes of Stalingrad, a World War 2-themed tactical shooter, is available for free. Like Valve did with Left 4 Dead 2 some months ago, the game is yours to keep forever as long as it's added to your Steam account within the giveaway period.

Tripwire Interactive will parlay its gifting mood into a free Steam weekend featuring Red Orchestra 2's Rising Storm expansion. During the free trial period of the expansion, Rising Storm will be available for purchase at a discounted price.

To grab Red Orchestra 2 for free, simply "add" it to your account from the game's Steam store page. Tripwire's shooter is regularly priced at $9.99.
[Image: Tripwire Interactive]

This article was originally published on Joystiq.