I am wondering if Noel "topped off" the oil level recently? It is a classic symptom of overfilled oil. On a Griso the top mark is TOO much.
Exactly...it will blow oil thru the two drain tubes down below and also accumulate into the airbox. I'd siphon off 1/2 a quart to start with, clean up the box and drain the tubes and see if it continues to accumulate, then drain some more. As long as the bike is running...he might need a fresh set of plugs if they got fouled...I'd try all that before towing, could be an easy fix.
Presumably it's a low mileage bike and as Dave says...the result of a fresh oil fill...