Licensing derivative work of forked code base

Question

What I have done

There's PHP tool which uses Bitbucket API to deploy code on environments without Git etc. It's licensed under GPLv2 or any later.

Bitbucket API is shifting from v1 to v2, and it's impossible to achieve same thing with API v2 just by design - it doesn't allow to get code of individual files.

I have created my own workaround version, added features, cleared up spaghetti & WET code etc, So ending up heavily rewriting original code - only 40 lines of two helper functions have stayed intact and even then those two functions maybe was found online as examples.

The thing is I want to release it as my project (complying with original licence)

1. Would it be fair if I rewrite readme.md stating it's my own, but referring that was inspired by what original work.

2. Should I keep doing it on forked project or should I take down fork and release it new clean repository?

3. Is it o.k. if I continue original versioning with new major version, or should I start everything from zero?

Answer 1

GPLv3 would certainly consider your actions as requiring that the project remain under the GPL:

To "modify" a work means to copy from or adapt all or part of the work in a fashion requiring copyright permission

GPLv2 doesn't define modifications except including translation among them. But your work is a derivative work in any case and must remain under the GPL. Perhaps you were aware of this, but it seemed there was an implicit question over whether you could license it however you want.

Would it be fair if I rewrite readme.md stating it's my own, but referring that was inspired by what original work.

As long as you mention the original author's copyright over the original work, saying something like "This project is a fork and by-and-large a rewrite of [other project], copyright [year] by [other project's author]". It can't hurt to reproduce the original readme as well; attribution is a good thing.

Is it o.k. if I continue original versioning with new major version, or should I start everything from zero?

I recommend that you keep the version control history of the old project intact, as this aids with the attribution requirements of GPLv2 section 2a:

You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.

and GPLv3 section 5a:

The work must carry prominent notices stating that you modified it, and giving a relevant date.