Is it fair/legal/ethical to call a derivative work/project fork/based-on software your own name/logo/brand?

Please don't answer unless you really know for sure. I need a credited/reliable opinion.

Thanks in advance!

The three triplets of words are coincidental, by the way.

It all depends on what the nature of your product is and the user license included with the software.

If you are building a plug-in for another piece of software, it is okay as long as you clearly have disclaimers stating that the original software and its logos are a trademark of the other company.

If you are modifying an open source (GNU / GPL / Mozilla / other open or semi-open license) then generally it is okay as long as you include the license with your software and read it carefully. You can modify an open source code and keep it private or you can publish your software using the open source license as well. The open-source community generally also likes for you to say what projects your software is based on.

If you hacked or took source code from a private project, then no it is not okay unless you get written permission. This will likely require lawyers.

If you are taking a whole piece of software and bundling it with your own software on top, it may or may not be okay. Read the license. Most licenses do not allow rebundling of their software. Some do though.

Regardless, of what you are doing the first step is always to read the License in its entirety! If you intend on using the software for commercial purposes or plan on selling or distributing the software or plan to sell services for the software you need to talk to some lawyers.

Yes/no/maybe?