You can get bpython by downloading the latest release, cloning the mercurial repo or using your system's package manager.
bpython has the following dependencies:
The development version is available with git; use the following command:
git clone https://github.com/bpython/bpython/
If you get stuck, join #bpython on irc.freenode.net or send an email to the mailing list (more info).
If you have easy_install or pip on your system (and you probably have) you can install bpython through PyPi.
(Note that packages may be out of date so please try at least the latest release if you have any problems before reporting bugs).
Terje Rosten has informed me that bpython is now in fedora, so "yum install bpython" should be all you need.
bpython is included in the ubuntu repositories starting at Ubuntu 9.10 karmic koala.
This is an old version, please consider installing from tarball.
Pascal Bleser has been kind enough to provide a package for OpenSUSE, which can be found here:
Apparently you can also add this repo:
to your package manager, if someone would like to submit the exact instructions for that, feel free.
You can find bpython packages for Solaris on the sunfreeware website, kindly provided for by Steven Christensen.