Yuki's Vacation Trivia (Windows)
James Silva released this game as open source a short while before he released his Blood Zero game. In his own words (in the readme file) "people have just been bugging me to release something, so here's your freeware." He also explains that he "did this because people always ask me how I make games; this may be a bit of a clue in for people who have some programming ability. However, if (for some strange reason) someone decides to put their own name on it, add a couple levels, and sell the thing I'm gonna be fucking pissed."
He admits, though, that the game wouldn't be of much help for those who don't have any experience in programming because the commenting is poor and he didn't even remembered how the game worked, as he had released it six months after having worked on it.