The add-ons mentioned in this document are licensed under the GNU General Public License (GPL). This means you are free to use, modify and distribute these add-ons, as long as you distribute them under the same license. You have the right to study and modify the source code to meet your needs. Any modifications you make must also be licensed under the GPL.
The key principles of the GPL are:
Freedom to use: The license allows anyone to use the software for any purpose, without any restrictions.
Freedom to study: The license allows anyone to examine the source code of the software to learn from it.
Freedom to modify: The license allows anyone to modify the software and distribute the modified version.
Freedom to distribute: The license allows anyone to distribute the original or modified version of the software to others, as long as they also distribute it under the same license.
Copyleft: The GPL is a copyleft license, which means that anyone who receives a copy of the software and modifies it must make the modified source code available under the same license.