Bareflank is described by its GitHub page as:
The Bareflank Hypervisor is an open source, lightweight hypervisor, lead by Assured Information Security, Inc. that provides the scaffolding needed to rapidly prototype new hypervisors. To ease development, Bareflank is written in C++, and includes support for exceptions and the C++ Standard Template Library (STL) via libc++. With the C++ STL, users can leverage shared pointers, complex data structures (e.g. hash tables, maps, lists, etc…), and several other modern C++ features. Existing open source hypervisors that are written in C are difficult to modify, and spend a considerable amount of time re-writing similar functionality instead of focusing on what matters most: hypervisor technologies. Furthermore, users can leverage inheritance to extend every part of the hypervisor to provide additional functionality above and beyond what is already provided.
Bareflank is more of a framework for building complete hypervisors like you'd expect from Xen or VirtualBox or as the developers say "any type of hypervisor." Bareflank is licensed under the LGPL v2.1.
More details on Bareflank via the ainfosec.com announcement.