Private Packagist http://drupal.org/node/3409795

Private Packagist is a Composer repository for your company available as SaaS or on-premises: Easy Composer access to internal packages on GitHub, GitLab, Bitbucket or any VCS and mirrors of all your third party dependencies.

Private Packagist simplifies working with dependencies on client projects by providing Security Monitoring, Update Review, and separating customer specific packages into Composer subrepositories.

Best of all, Private Packagist is made by the maintainers of Composer and packagist.org, so your subscription helps fund their development and Private Packagist always supports the latest Composer features.