One of the things you’d expect from an active open source project is that the code base is likely to grow as more and more features are added. In An exploration of open core licensing in network management I mentioned that one possible side effect of open core software is the creation of a functionality ceiling. A functionality ceiling is a level of functionality beyond which the community edition product manager is unwilling to implement because of the fear that the enterprise product will be less attractive to potential customers.
Open core refers to a business strategy employed by some commercial open source companies. The open core strategy is popular amongst companies within network management. The open core strategy is largely defined by creating an open source community product that is freely given away, and another product, the enterprise edition, that is sold as a regular commercial software product. The open core business model is useful to software vendors because it permits them to build a community surrounding the open product who will form the nucleus of the people who upgrade to the enterprise product.
A real world example of what Tarus Balog from OpenNMS has been banging on about recently with his critique of open core or fauxpen source. A product manager who has an open product and a closed product plainly has a decision to make over which features go into which product. Give too much away and the value add of the closed enterprise product is insufficient to warrant the licence fees. Put too many features into the enterprise product and the open source offering becomes useless.