Digital musical instruments enable new musical collaboration possibilities, extending those of acoustic ensembles. However, the use of these new possibilities remains constrained due to a lack of a common terminology and technical framework for implementing them. Bf-pd is a new software library built in the PureData (Pd) language which enables communication and cooperation between digital instruments. Its design is based on the BOEUF conceptual framework which consists of a classification of modes of collaboration used in collective music performance , and a set of components which affords them. Bf-pd can be integrated into any digital instrument built in Pd, and provides a " collaboration window " from which musicians can easily view each others' activity and share control of instrument parameters and other musical data. We evaluate the implementation and design of bf-pd through workshops and a preliminary study and discuss its impact on collaboration within improvised ensembles of digital instruments.