Freeciv is a Free and Open Source empire-building strategy game inspired by the history of human civilization.
https://www.freeciv.org/
If you want to report a bug, contribute a patch, or just open a wishlist ticket, go to https://osdn.net/projects/freeciv/ticket/ (and "Submit New Ticket" on the right) In case of a (code) contribution, you should see https://www.freeciv.org/wiki/How_to_Contribute first.