If you are a student, you do not need a license to run Genymotion Desktop for your studies.
If you used the trial version, Genymotion Desktop should prompt you to either buy a license or switch to personal use only free version after 30 days.
You may need to sign out and in again: go to Genymotion > Settings > Account > SIGNOUT.
Genymotion free is for personal use only. You must not share your account with other students, or use Genymotion on a public device such as a school computer.
However, if you plan to use Genymotion Desktop for commercial or professional use, such as developing and selling an application, you must buy a license after the 30 days trial period, as stated by our conditions of use.
For more details about paid licenses, please read our pricing page.