Not really independent. Ole Tange tried to get his 2nd parallel into findutils (to replace xargs and allow parallel processing) in 2005. Because it was written in Perl, findutils refused to add it. So Ole Tange contacted moreutils in 2009, but they never answered, but later one guy of them, Tollef Fog Heen, rewrote parallel in C, with just minor API discrepancies. They say it predates GNU parallel, because the 2005-2007 package was not a GNU project then. It was added to savannah as individual GNU project in 2010, Ole gave up inclusion into findutils then.

moreutils parallel was written 2008, and added to moreutils 2009, just when Ole asked them. https://git.joeyh.name/index.cgi/moreutils.git/commit/?id=0f...

https://www.gnu.org/software/parallel/history.html

Hence I called it a "fork". Independent, yes, but when you know about the project, steal its name and put it into wide distribution under that same name, because you think your name has a better chance of being adopted, this is called a fork. Like a pitchfork. Poking into the original authors eyes with a sharp instrument.