More options for permission and usage rights

Change the radio buttons to checkboxes, so different usage cases can be selected.

Add commom licenses like GPLs etc.

Further add options like:

• Allow download on other model pages

• Only free generation services

• Ask for permission to use on other model pages

(something like that) I'm not really into law and rights stuff, but maybe there's some option to add.

Background: I want a minimum of control where my models are published and used, even if they are freely available.