There 'should' be no oil in the clutch housing, probably its either the o-ring or the engine output oil seal. Its best to replace both if in any doubt. It could also be from the transmission input shaft seal, but from your pictures that doesn't look likely (transmission oil smells different too).
As I found, with the transmission out its a good time to replace that breather hose as access is easier - it attaches to an oil separator inside the air filter box. This leaking would not introduce oil to the clutch housing but it will mess up the engine fuelling due to air getting onto the induction system where it shouldn't.