Partially or fully biosourced (co)polyamides have been prepared from commercial (11-aminoundecanoic acid, octadec-9-en-1,18-dioic acid, dodecan-1,12-diamine) and/or an original branched and unsaturated ((9Z)-octadecene-1,12-diamine) monomer. Undec-11-enoic acid was used as chain limiter in order to obtain controlled average number molecular weights around 7000 g mol−1. By varying the relative composition of monomers and/or the amount of side chains and/or the amount of unsaturated repeating units, copolyamides exhibiting low glass transition temperatures ranging from −31 to 3 °C and low melting temperatures ranging from 60 to 143 °C have been obtained. The branched monomer was found to act as internal plasticizer. Coatings have been prepared from these polymer materials at their melting temperatures. The presence of carbon–carbon double bonds on the polymer backbone allowed their photocrosslinking in the presence of benzophenone. This UV curing enhanced the hardness of the obtained coatings. These polymers are therefore expected to be used as bio-based UV powder coatings for heat sensitive substrates.