Paint.net was originally MIT licensed but the author closed its source because people did not give him credit. Note: The MIT license does not require credit.

https://blog.paint.net/2007/12/04/freeware-authors-beware-of...

Paint.net likely still benefits from the announcement of "Open Source Alternative To Microsoft Paint" long after switching to a proprietary license, which I find more dubious than using MIT-licensed code without giving credit to the author.

Also I rather doubt a "clean-room reverse-engineered rewrite of Direct2D" can be "written by our good friend Claude, without whom this would NOT have been possible"?