For those with an Xbox Live Gold subscription, 'Splosion Man is now free.
It is also backwards compatible on the Xbox One.
If you don't have one, the cheapest Gold subscription can be bought for $10.95 (for a 1-month card) at any Coles/Woolies, the three big department stores and at EB/JB. It will nab you this game, Mirror's Edge (this month's 2nd 'Games with Gold' game) and the next two 'Games with Gold' games (one on the 1st and the other on the 16th of October).
Love Splosionman