Minecraft wiki entry for Development_versions, associated text: Value can be defined as false / true. All rules except keepInventory are true by default. The available rules are as follows:
doFireTick (false=fire cannot spread)
mobGriefing (false=creeper explosions do not damage blocks)
keepInventory (true=keep inventory on death)
doMobSpawning (false=mobs do not spawn)
doMobLoot (false=mobs do not drop loot)
doTileDrops (false=blocks do not drop items when breaking)