I would clean that up, then drive it and see where it is coming from. Once it has been blown around like that it is hard to know what the original source is. While normally fluids only drip down, it can be surprising where fluids go once airflow is applied. It could be the breather tube has come off and it is from that. Or it could be from the seal for the diff cover. It does not look to be coming from the pinion seal, which is good. Also, coming from the pinion seal usually means oil is being thrown by the input hardware. So you will typically find oil splattered around the pinion 360 degrees. I don't see that happening.
Noticed this too, could be from one of those EVAP/Fuel lines above it.
Otherwise I also agree with others that it's most likely the diff cover seal. You'd be surprised how many people can't install those seals, or use gasket maker correctly.