I would like to find out whether I can add extra functionality to the GUI and whether this would violate any licensing? I do not want to modify logos and/or change the names etc as I know this requires OEM program. What I am after is, I have a piece of software that generates statistics for Asterisk System and I wanted (for ease of our customers who use FreePBX) to have a button in the header that will take them to the software dashboard, and perhaps create an additional page within FreePBX UI where a user will be able to modify various settings that relate to the statistics software. Also, I was thinking about creating a simplified dashboard (as the current one is not very appealing) - Could this also be done?
Mind you no existing features will be changed and/or removed. Only new added which are relevant to what we do
You simply need to abide by the terms of the license (typically GPLv2/GPLv3) with code you use. Most of this revolves around leaving credit/copyright notices and releasing modified source if you distribute covered code. I am not a lawyer so I can’t tell you what is or is not ok but there is a FAQ https://www.gnu.org/licenses/gpl-faq.en.html