I contacted mojo about this and they said thats how its meant to be. (obviously not meant to leak if your bike’s upside down but oil on the stanchion after use is normal)
edit: heres the email response from Mojo…
“What your experiencing is normal, we often find after doing dust wiper seal maintenance that the Float fluid will show on the stanchions, this is what the dust wiper seal is designed to do; keep the dirt from getting in to the lowers and effecting the internals. It is important to stay on top of thew maintenance after every 15 hours of use. We recommend using the 10wt green suspension fluid available here – http://www.mojostore.co.uk/acatalog/Fox_Fluids.html.”