All OOTP Developments games can be activated on up to two computers simultaneously. If you want to activate on a third computer, you have to unlicense the game from one of the computers that you have that are currently activated. You don't have to uninstall the game from that computer - deactivating (unlicensing) is sufficient.

Additional licensing questions are answered below:

1. All activation errors/issues can be resolved here.
2. I lost my license number and confirmation email.
3. Unlicensing your game.
4. Installing the game on more than two computers
5. Can I use my PC license on Mac/Linux machine, or vice-versa?