Through his non-profit LILA in France, he has assembled 6 artists to produce works specifically for this calendar (Disclaimer: I'm one of the artists):
The proceeds from the calendar will be split evenly between the artists, the LILA non-profit, and various F/OSS projects that the artists used (GIMP, Blender, Inkscape, etc...). The full list is on the site. (Second disclaimer: I'm deferring any of my proceeds to the projects).
This is a really nice way to donate a bit to the various projects and get a neat gift for it.
Head over to the site to see some sample images from the artists, and consider buying a calendar! Jehan is looking to meet a minimum order before moving forward (around 100 I believe).