Our official stance is that if you’re going to use it for a bunch of people then it’s probably best to have each person buy one. But we don’t do DRM and there’s nothing preventing you from using our stuff multiple times across multiple computers.
So if you’re going to do that, we’d ask that you try out our trainers, and if you really like them and get good results from them, then please tell your friends. If you get three friends to buy our stuff then you’re karmically in the clear. ;-)