ConcourseSuite CRM doesn't fit into any of the approved licenses on SourceForge. Concursive has the Centric Public License which permits anyone to download and make changes for their use, but not to redistribute the crm with changes themselves. However, your changes can be licensed in any way you want and distributed separately. Most OSI licenses require the code contributions to be the same as the license which makes it difficult to add proprietary extensions to the CRM -- like integrating with ERP or lead sourcing systems.
Any community member can also contribute code back to Concursive so that the code can be maintained in future versions.