The Symphony IDE was originally developed as part of the EU FP7 COMPASS research project.
The COMPASS consortium is a group of researchers and companies committed to collaborative research on model-based techniques for developing and maintaining Systems of Systems (SoS).
— From the COMPASS website: http://www.compass-research.eu/
Current development is ongoing, but at a necessarily slower pace as the COMPASS project has finished. We hope to pick up the pace of development with new research funding, however, we will happy accept all contributions –bug reports, fixes, and so on– in the meantime.
Symphony is developed as an extension to Overture, which is available at http://overturetool.org/, and its source is available on GitHub at https://github.com/overturetool/overture.