It isn't a BOSS Mustang, it is being sold as Saleen/Parnelli Jones Limited Edition Mustang. (well, actually, it isn't selling well at all from what I hear).

BOSS was a Ford product, but built by Kar-Kraft. The 302 was used to win the '70 Trans-Am title. And the 429 was basically the Nascar engine for drag racing.
http://www.bossperformance.com/history.htm

However, Larry Shinoda was the designer for Ford and responsible for the BOSS models and his company owns the BOSS name (he passed away).
http://www.teamshinoda.com/about_us.htm