Following the release of Matpower 6.0, the Matpower project moved to an open development paradigm, hosted on the Matpower GitHub project page:
The Matpower GitHub project hosts the public Git code repository as well as a public issue tracker for handling bug reports, patches, and other issues and contributions. There are separate GitHub hosted repositories and issue trackers for Matpower, MOST, MIPS and the testing framework used by all of them, MP-Test, all available from https://github.com/MATPOWER/.