Forge version 43.2.13
Friendly Fire version 14.0.4
Open Loader version 15.0.1

Villagers still receive damage from player.

FriendlyFire-Configure-1.0.0.zip

I create a new pack include only Friendly Fire and Open Loader, and your pack works. But my original pack isn't. Maybe you are right, but I don't find the mod yet.

Are you certain your data pack is being loaded properly? This example pack works fine for me.
FriendlyFire-Example-Pack.zip

Are you certain your data pack is being loaded properly? This example pack works fine for me. FriendlyFire-Example-Pack.zip

Yes, it's loaded correctly, but don't work.

Did you try with the example pack? If the pack I gave you does not work then the pack has not loaded correctly or one of the mods is interfering. One possible explanation is that a mod is replacing villagers with their own villagers so the ID is not the same.