Paint.net used to be an open source collaboration project by Rick Brewster, a Microsoft Employee and the students at the University of Washington. Today it is a private closed source project accepting donations, and still headed by Rick Brewster.
It’s lighter, simpler, and faster with a much more intuitive UX. for basic image manipulation tasks it’s awesome.
For creation of art I’d use Krita, it is more feature complete. But if Paint.NET appeared on Linux, I’d use it in a heartbeat.
Paint.NET is closer to Gimp, but usable.