Once the free trial has been installed and activated, you will not have the ability to deactivate or put the program onto another computer. The full retail version allows two activations and the ability to deactivate and reactivate as needed.
If something happens to your computer (crash, lost, stolen, etc.) you will not be able to receive another free trial.
If you have activated using a Trial number (KFDV) instead of your KFDX number (the 18-week EDU trial) and you need to activate for 18 weeks, follow the steps in this article: How do I change the Customer Number embedded in Final Draft?