If you sell on Steam, you are not supposed to have a limited activation system. With steam no one cares how often I activate, since there is another limit ... I can start my applications only once at a time. So software is tied to my account and not computers. The Steam model is that you can have only one Steam instance active. I cannot activate my 3D Particle edition anymore !!!! It tells me I activated too often. I change computers very often, so that is why I buy all software I can and need on Steam to NOT have this problem.