Barry,
Unity 3D is a game development tool, of which there are free and pro versions. The software isn't being developed by Perfect Parallel as it is already out there and they have opted to use it to build Perfect Golf.
You can get a download of the free version here - http://unity3d.com/unity/
Course Forge is what in the Unity 3D world is known as an Asset Tool. It is a bolt-on which you download and use in conjunction with Unity 3D. Course Forge allows you to layout your course and set the tees and pins to make the course playable. The rest of the design process is effectively done in Unity 3D.
So yes, if you are a budding course designer, it is worthwhile taking the time to learn how Unity 3D works, how to sculpt terrain, add objects, add skyboxes, place light sources etc. as once Course Forge becomes freely available to the community, with a knowledge of Unity 3D you are well on your way to being able to create courses.