What does turning off mob griefing actually do?
The mobGriefing rule affects the following:
- Mobs trampling farmland
- Mobs picking up dropped items (zombies, villagers, etc.)
- Zombies breaking doors
- Sheep eating grass (sheep will still regrow their wool, but the block will not change from a grass to a dirt block)
- Villagers harvesting/replanting farmland
- Dragon destroying blocks
- Wither explosions destroying blocks (both initial explosion and witherskull projectile)
- Creeper explosions destroying blocks
- Endermen picking up blocks
- Silverfish hiding in stone (Silverfish will not reinhabit stone blocks after roaming)
- Silverfish calling for help out of nearby blocks destroying said blocks
- Snowmen leaving snow traces
- Rabbits eating crops
- Blaze fireballs creating fire
- Ghast fireball explosions destroying blocks
(the above was taken from the game code)
From what I've experienced this rule includes only destruction by force and interactions. That said, I am sure mobs stepping on farmlands will not be affected by this game rule. I have no written source for that, though.
Also this rule affects only specific actions including villagers picking up things. So yes, it does affect non-hostile mobs as well.
What it does affect:
- Creeper explosion block damage
- Wither, Ghast & Enderdragon block damage
- Zombies kicking in doors
- Enderman block thievery
- Villagers taking items
What it does not affect:
- Creeper damage to Entities (an item frame will still be a goner)
- Mob damage to other individuals
- Mob behavior (unless you want to count in Zombies knocking on your door)