Yes - The Active Reader is a Unity plug-in, so you will need a copy of the Unity 3d game engine.

The Active Reader will work in both the free version of Unity (commonly referred to as the "Indie" version) as well as the full, professional version of Unity (the "Pro" version).

You can download Unity for free from the Unity website here:

www.unity3d.com

After you have Unity, you can upgrade your license to a Pro license if you decide that license will best suit your needs.

Note: As of ARTool2_42d, the currently supported version of the Active Reader is Unity 3.4. Unity 3.5 is still in Beta and is not currently compatible with The Active Reader