> Nulis is an open source tree editor for writers, inspired by Gingko. To learn how it works, visit https://nulis.io/about and try it out.

He does say "inspired by", though not sure if that was the credit you are expecting.

I think that's plenty of recognition. Most people wouldn't even bother out of fear of losing potential users to the "original".

Unfortunately, being the first or most common product in a space has the side effect of attracting copies, spin offs, or other imitations.

It's in like the first sentence of the Readme.

> Nulis is an open source tree editor for writers, inspired by Gingko.

I will say that it's not mentioned anywhere on nulis.io however.

Ok, glad it's mentioned somewhere.

Couldn't find any mention first time I checked it out.

I think it's absolutely acceptable to ask for more references if you feel it's insufficient.