I did not make this flag, but I found in on CKAN. It was one of the first mods I ever installed.
It was created by hakan42 and is included under the CC-BY license.

I don't think anyone else in the entire world knows about this flag, and hakan42 was last seen on curseforge 10 years ago.
I sent him a message on curseforge, but i don't know if he'll ever get it. Maybe one day I'll get to talk to him.

I have now since adopted it as the logo of my space agency, in tribute to this long-forgotten PNG of a rubber duck.