David Lara sent me an email about a very old school game he ported named L’Abbaye des Morts .
The 2d platform game is freeware and the ported and rewritten game is also under the free source  GPLv3 license.

An obsolete videogame for a dark passage of history
In the 13th century, the Cathars, who preach about good Christian beliefs, were being expelled by the Catholic Church out of the Languedoc region in France.
One of them, called Jean Raymond, found an old church in which to hide, not knowing that beneath its ruins lay buried an...