That seal is just seeping or weeping. Warranties (factory or aftermarket) define a "leak" as having a drip. Without a drip, there really isn't any loss of fluid, so it doesn't consitute needing a repair.

Honestly, if I were you, I'd just clean it up and keep an eye on it. If it drips, get it repaired.

Think about it like this...... If the guy replacing the seal messes up when torquing the pinion nut (too much or too little), you will later have a pinion bearing failure, and need a differential overhaul. And I've seen this happen way too many times over the years, unfortunately.

 

my front axle housing is "seeping" on my truck. on the passenger side where the cv axle bolts on. i changed the fluid once myself, and have never noticed any fluid on the ground or on the underside of the truck anywhere, but it does have a slight whining noise when driven in 4wd. sound did not change after the fluid was changed.