According to wikipedia this is related to the AMOS-2 staelite leased by Facebook to provide internet coverage in part of Africa.

An interesting clause in their contract is:

"The parties have agreed to the right to terminate the contract if Amos-6 and the ground gateways in France, Italy and Israel are not ready for service by January 1, 2017"

So this fire could have wider repercussions if SpaceX doesn't get a new launch ready in time. (Unless that same contract also has a clause about SpaceX failure vs IAI failure.)

> but it's still liquid, so you can't just vent it off.

You can vent off liquid to keep the pressure down, but since it's heavier than air it will just add to the fire. Unless maybe they have some sort of piping system connected to the vent to route the extra fuel elsewhere.