““Open core/hybrid source Probably the most common model today, open core describes an open source project that is partially, even mostly, open source, but with some portion of the project or some features remaining proprietary. Typically there is a basic level of functionality — referred to as the core — which remains open, and proprietary features or capabilities are added upon and around this. The highest profile example of this model today is Hadoop. Cloudera, the first organization to commercialize the data processing platform, contributes along with other organizations, commercial and otherwise, to the base Hadoop project, which is open source. A proprietary product that includes management functionality is then sold to customers on top of the base open project. This model is viable, but can be difficult to sustain. One of the challenges for those adhering to the open core model is that the functionality of the underlying open source project is evolving at all times, which means that the proprietary extensions or features must outpace the development of the open source project to remain attractive to customers.””
