Bitcoin is an experimental new digital currency that enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate with no central authority: managing transactions and issuing money are carried out collectively by the network. Bitcoin is also the name of the open source software which enables the use of this currency.
The software is a community-driven open source project, released under the MIT license.
OS X 10.6 or later
(Via MacUpdate - Mac OS X.)