You may offer payment for done work, installation and support.
However there are certain restrictions that apply:
- The person is allowed to distribute your modifications under the rules of GPL
- The person must be informed that the system is a derevative work of or a full version of CPG-Nuke and that it is copyrighted using the GNU GPL and that comes without any warranty and that it's freely available at cpgnuke.com
Your new own coded files are no derevative work and can be handled as seperate works BUT since your files interact with CPG-Nuke and can't work without CPG-Nuke they are in a "gray" area to be GPL or not. This could give trouble IF the person reads the license and you must tell exactly why your files have a different license.
In CPG-Nuke 9.0 this issue will be handled properly but NOT in any previous release.
Server specs (Server OS / Apache / MySQL / PHP / DragonflyCMS):
Fedora 25 / Apache 2.4.27 / MariaDB 10.1.26 / PHP 7.1.10 / Mercurial