Re: bustabit.com -- The Social Gambling Game (formerly moneypot.com)
I'm not sure it is any more, but an old version of the source is available. I think some anti-spam or anti-DDoS measures were added "in secret" to make it harder for attackers to circumvent them.
Yeah, because of some abuse (and the abusers watching the open source changes to continue to abuse) I made it closed source, but you can still access the old version. Things like the bonuses and core mechanics of the game are unmodified.
And making the later versions closed source has been a decent revenue stream, I've sold a whole bunch of licenses to sites (especially csgo ones) for 2 BTC a piece =)