The DIRAC interware is a complete Grid solution for one, or more than one community of users that need to exploit distributed heterogeneous resources.
DIRAC forms a layer between a community and various compute resources to allow optimized, transparent and reliable usage. The types of resources that DIRAC can handle include:
Computing Resources, including Grids, Clouds, HPCs and Batch systems
Many communities use DIRAC, the oldest and most experienced being the LHCb collaboration. Other communities include, but are not limited to, Belle2, ILC, and CTA
DIRAC source code is open source (GPLv3), written in python, and hosted on github.
An alternative description of the DIRAC system can be found in this presentation