WordNet sense 1 (involving the joint activity of two or more):

combined, concerted, conjunct, conjunctive, united

WordNet sense 2 (a jointly owned commercial enterprise (usually organized by farmers or consumers) that produces and distributes goods and services and is run for the benefit of its owners):

co-op

WordNet sense 3 (accomplished by collaboration):

collaborative

WordNet sense 4 (willing to adjust to differences in order to obtain agreement):

accommodative

WordNet sense 5 (not involving competition or competitiveness):

noncompetitive