Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Dear Ismail,
As an Independent Advisor and community user, I'll help you with your question.
Yes it is legal, you can use Deployment Tool to install your Office version, at some point it will ask to use your own Activation key in order to activate it, so if you don't use a key some features it will not work and probably it will totally stop working at some time.
Regards,
Renzo.