A rather interesting concept is d0x3d! (a network security game):
It is actually intended to be a sort of teaching aid (ideas how to use it in class here), but it seems interesting enough to play with friends and relatives too.
You can order a full version of the game or download the sources under the sadly more restrictive CC-by-NC-SA here.
A similar concept of combining teaching with playing is the trading card game Phylo. Sadly it is even more restrictive in licensing (CC-BY-NC-ND), thus I am stretching it a bit to mention it here.
Much more open (and mentioned a few times before on FG) is Wtactics:
Wtactics card examples |
Not much updates for it lately, but I am still looking forward to have in playable in their under development web-based client or Wagic.
Another nicely licensed (CC-by-SA) but update-lacking open-source board game is Sovereign:
Sovereign game board |
One such general system is VASSAL, a FOSS engine to build and play online adaptations of board games and card games. It makes it possible to play live on the Internet or by email and has a quite extensive library of (mostly propitiatory) game modules.
VASSAL game module example |
Definitely also worth mentioning in this context is TripleA, also a RISK like game that recently had a rather big update and now includes a new map-creator for example.
TripleA, new WWII worldmap |
But if you know of more cool examples of these kind of crossovers between FOSS computer gaming and table-top games, please comment below!