Looks to me like a little bit of heat may be the answer. Gently heat the fork leg with a torch around the lug where the thread is. With aluminium having a higher coefficient of expansion than steel, the corrosive bond will let go. After the heat is applied try and break the bond by trying to turn the axle, once it breaks loose, apply some WD40 or similar and work the axle until she starts to rotate and unscrew.