Good question, Lydia! I always thought this episode took place at night, after everyone (except Jason, of course) finished work for the day. Maybe Willie has already performed his goulish task for the evening and therefore is at liberty. If--as I think it is--this is the first time he's been to the BW since opening the coffin, he is probably desparate for some kind of human contact in town. Also, Barnabas may have lengthened his leash a bit to prepare the good people of Collinsport and those at Collinwood for the fact that Willie isn't leaving after all and is now working for him (B.C.).