The Collaborative International Dictionary of English v.0.48:

neighbour \neighbour\, neighbouring \neighbouring\,
neighbourhood \neighbourhood\, neighbourly \neighbourly\
   Same as neighbor, neighboring, neighborhood,
   neighborly. [Chiefly Brit.]
   [PJC]

WordNet (r) 3.0 (2006):

neighbourly
    adj 1: exhibiting the qualities expected in a friendly neighbor
           [syn: neighborly, neighbourly]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "neighbourly":
   affable, agreeable, amiable, civil, companionable, considerate,
   cordial, courteous, friendly, genial, gracious, harmonious,
   helpful, kind, kindly, sociable, social, thoughtful, warm,
   well-disposed