The source code of the ISA² Interoperability Test Bed software is maintained on the European Commission's CITnet Bitbucket server. In June 2018 CITnet updated its policy for publicly shared code repositories to restrict access only to users with CITnet accounts. As a result, and to continue the open-source nature of the ISA² Interoperability Test Bed software, its source code is now mirrored on GitHub.
The Interoperability Test Bed's GitHub repository is synchronised for each release to include all release tags (current and previous) and have its master branch match the latest source code. Development and maintenance continues nonetheless on CITnet's Bitbucket server. Finally, note that the Interoperability Test Bed software is based on the GITB proof-of-concept implementation, the source code of which is also available on GitHub.