If Enderzoo http://www.curse.com/mc-mods/minecraft/225247-ender-zoo is installed Creepers still cause block damage with the game rule mobGriefing set to false. However enabling mobGriefingOverride in the config and disabling the block damage there works as expected.

Enderzoo adds custom Creeper variants and allows customizing of spawning behavior. This might cause trouble with the transformations of this mod.

Reproduced in a fresh 1.7.10 install with latest forge (10.13.3.1403), Enderzoo 1.7.10-1.0.15.32 and Sprinkles 1.7.10-1.6.0. Configs are unchanged. Removing either mod causes the gamerule to work as expected.

EDIT: Just to clarify I am talking about the Vanilla Creeper, not the modded ones.