All code-based products on Blender Market are licensed either under the GNU General Public License, commonly known as GPL, or as MIT.
The basis of the GPL license is the freedom for non-restricted use of the said software:
Nobody should be restricted by the software they use. There are four freedoms that every user should have:
- the freedom to use the software for any purpose,
- the freedom to change the software to suit your needs,
- the freedom to share the software with your friends and neighbors, and
- the freedom to share the changes you make.
Further details and the license text may be found here: http://www.gnu.org/licenses/gpl-3.0.html