You are looking at the wrong number :) That's the total amount of forks on GitHub. Whereas only 15 of them had any commits by people who forked the repository. Among those 15 people:

- One is a regular GIMP contributor.

- One couldn't wait another day for a macOS build of version 2.10.12.

- One patched file association on Windows and submitted his patch to the upstream project.

- Some of the others worked on their pet peeves, and some of them discussed it on the upstream bug tracker.

You might want revisiting your definition of a fork :)