Ecosystem Network Effects
One of the most heartening signs of maturity within the open source world - both literally and metaphorically - is the growing number of project tie-ups. The latest is Trolltech, which has integrated Qt, its flagship C++ based cross-platform development framework, with the popular Eclipse Integrated Development Environment (IDE). The C++ integration augments the integration currently available for Qt Jambi – a version of Qt for Java development.
This is a network effect, but writ large, at the ecosystem level.