Add a license to the application

[AIDaniel]

There are multiple choices for licensing a software.
I do recommend if you want your software to be free in its right to opt for a free license model.
This type of license will allow your existing software to be redistributable and reused by other people for free BUT will FORCE that any by product of your work (derived from your code) to also be FREE software and not be able to be integrated in any kind of commercial paid software.

For more information regarding licenses please see the following link:
https://www.gnu.org/licenses/license-list.html

[tuxayo]

BUT will FORCE that any by product of your work (derived from your code) to also be FREE software

Note that we are talking about free as in freedom. And that concept of forcing the software to stay free/libre is called copyleft.