Copyright and author issues

I've taken an extension from the repository and made improvements on it and while doing it I rewrote almost every line in the module and made several changes in the parts that have a predefined structure (dca and config files). Of the original extension the idea remains and the functionality has become much more.

Now what does this mean to the copyrights and the notices I have to put in. For as far as I'm concerned nearly no material of the original author remains and most part is my own. The license GPL was defined. The original author cannot be reached, I tried and the extension does not seem to be updated (A good suggestion has been made months ago and was not included). I want to re-insert it into the extension repository as my own extension under another extension name.

Good question Ruud.
I'd like discussion on this too,

My answer to you would be we're an open source community, we all learn from each other, and as long we don't just take somebodys extension verbatim and say "I wrote this" - then to republish modifications in the repository under another name is fine. The point at which a modification becomes something new is difficult to define.

I figure as long as you are releasing under the same licence (GPL in this case) there is no conflict. If you were releasing it as a commercial extension then the question would be more difficult - it really would need to be an original work.

I think you've taken the right approach trying to contact him/her, but this to me is politeness rather than obligation.

As to copyright notices I'm not sure. (I'm also not sure whether an extension should/must have the standard Contao notice in it - maybe Leo could clarify this.) You could always say "by Ruud, based on the xxx module, thanks to yyy".

It would be good to hear opinions from people who have released extensions - either on the legal obligations or even on just how they would feel about someone taking one of theirs and forking it.