Hi
If you use "native" MS Kinect SDK driver then yes, you'll need two PCs. However, no license is required for recording with iPi Recorder. Thus you'll still need just a single (Basic) license for tracking recorded videos in iPi Mocap Studio.
Also, recent versions of iPi Recorder support libfreenect drivers for Kinect v2 which allow to
use multiple Kinect v2 cameras on a single PC.
There is a
comparison table for different licenses (editions). In a few words, dual Kinect setup allows to capture a wider range of motions (e.g. full turns).