MAIN QUESTION SUMMARY:

Can someone with real world experience, who has actually Modified, Re-Wrote, Re-Released and Re-Named Open Source GNU V3 Licensed software; please share their experience on the subject?

Background:

I have been working on and debugging a plugin (for an OpenSource CMS system) for 4 years (about 500 hr per year) in order to make it work perfectly.

• The plugin is licensed as: GNU General Public License version 3 [or later]
• The plugin clearly states: free software: you can redistribute it and/or modify

Over that time the following things have happened:

• The plugin developers have not supported the plugin very well or fast enough (in my opinion)
• I have added major new functionality to the Plugin using "extensions"
• I have patched the plugin repeatedly, for example:
• Upgraded from PHP 5.4 => 7.0 => 7.2 (cleaned up errors, rewrites, removed lazy code like faulty output buffering and is_array checks - ect...)
• Updated JS to modern web standards (Select2 3.5.3 => 4.0.2, jQuery 3.3, ect...)
• Continually added notes into the @package declaration and changelog
• Maintained and eventually modified the core plugin so much that its hardly even the same plugin anymore. (only 88 of 595 files are original plus 62 new files)

I am considering the following approach : (because I do not want to confuse people, this plugin accomplished the same goal but is no longer the same software)

1. Just rename the plugin
2. Honor the original developers by stating that this new plugin is "Based on the classic"
3. Keep the original License intact but in a separate .txt file
4. Keep the authors names listed as "Based on the work of"
5. Add a new GNU LICENSE declaration
6. Explain all modifications in a changelog
7. RE-RELEASE and RE-DISTRIBUTE the plugin under its new name
8. Go into the forum area where the original Plugin was distributed (where people are complaining) and tell them "hey, I had the same problems, so I rewrote this plugin get it here for free, cheers"

I now have the following questions and concerns:

• Is this acceptable and legal use of the GNU License? [I assume yes]
• Is this considered FauxPas or inappropriate? [I assume no]
• Should I not even mention the original name of the plugin? [unsure]
• Is keeping the authors names intact considered correct? [I assume yes]
• What is an honorable, noble and respectful way to handle naming? [want a professional opinion]
• How exactly does "Re-releasing GNU software after rewriting or heavy modification" work? [I assume I just rename it and write a declaration that explains the history of the code]
• Is there anyone with direct and specific experience in this exact same area that can share on the topic?
• Should the original plugin developers "rise from the dead" and see what I have done- should I be concerned? (I imagine its 50/50, they either see it and say good job carry the torch, or they may become irate)

IMPORTANT NOTE: some of the "extensions" for that plugin were not free, users had to pay to download them. I modified, maintained, updated and patches several of those as well. This explains some of my concerns here, there may be money involved on those extensions. These paid extensions also are listed ad GNU, version 2 or later

An example: I remember when Joomla was Mambo... I feel that this situation might be similar?

Research and notes: I have examined the following, which helped me formulate some of my assumed answers.

• https://opensource.org/licenses
• https://www.gnu.org/licenses/gpl-3.0.en.html
• http://www.gnu.org/licenses/
• https://odino.org/the-5-golden-rules-when-writing-open-source-software/ https://opensource.guide/legal/
• https://www.gnu.org/licenses/gpl-faq.html
• https://stackoverflow.com/questions/9493786/gnu-gpl-license-terms-open-source-softwares
• (Re-)formatting and displaying of software licenses/privacy policy/impressum
• https://law.stackexchange.com/questions/30278/can-you-use-only-the-name-brand-of-gnu-open-source-software
• Law and open-source project

Thank you for your consideration in this matter.