Yes, the title makes sense… with some explanation. Red Orchestra 2: Heroes of Stalingrad is free forever, if you add it to your Steam account at some point today. Once it is in your account, it is yours. The price will return to a non-zero value at 10AM tomorrow, April 24th, 2014 (I assume PDT). Of course, you should just launch Steam and add it to your account as soon as possible. The button suggests that you need to install it to your computer immediately, but you don't; it will just add it to your library.
This does not include Rising Storm, except the "rifle-only" access that has been available for Hereos of Stalingrad customers. To get the rest of Rising Storm, it will need to be purchased and, go figure, it is scheduled for a "free weekend" and a discount, this weekend. Clearly, Tripwire is hoping to increase sales of Rising Storm through the sum of these promotions.
To summarize the entire promotion:
- Hereos of Stalingrad can be added to your Steam account (if claimed before 10AM).
- With this, you can access "rifle-only" content for Rising Storm.
- This weekend, the full version of Rising Storm will be free until the end of the weekend.
- During that free weekend, Rising Storm will be discounted.
Honestly, there is little reason to not just add it to your Steam library as soon as you get a chance. From there, you can sit on it if you do not have time for it. It is such a small commitment.