PVS is a verification system: that is, a specification language integrated with support tools and a theorem prover. It is intended to capture the state-of-the-art in mechanized formal methods and to be sufficiently rugged that it can be used for significant applications. PVS is a research prototype: it evolves and improves as we develop or apply new capabilities, and as the stress of real use exposes new requirements.
PVS 6.0 is the current version. It is open source (under the GPL license), and we also provide pre-built binaries using Allegro Lisp (commercial), and SBCL (open source) for Linux and Intel Macs. See the download page for details.
PVS is one of the SRI FormalWare tools.