"Jigsaw is freeware and is free for private non-commercial use. It is not open source."

License:
Copyright 1996, Helmut Hoenig, Heiligenhaus/Bad Camberg
Permission to use, copy, modify, and distribute this soft-ware for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies.

2020-06-05
This comment came in via messages: "You have confused two different apps. Xjig is the original app which is open source Copyright 1996, Helmut Hoenig.
The other app is xjigsaw, which is a gui to run xjig." I have no idea about the game nor Linux games, but maybe someone can verify whether there is something to be fixed or not.