The generate.sh script is obsolete, but is included for historical reasons.
Maintained packages can be obtained:
https://github.com/Bitmessage/PyBitmessage/releases
Works on Windows XP or higher.
https://github.com/Bitmessage/PyBitmessage/releases
Wors on OSX 10.7.5 or higher
Releases matching PyBitmessage releases:
https://aur.archlinux.org/packages/pybitmessage-git/
Development snapshot equivalent to the v0.6 git branch:
https://aur.archlinux.org/packages/pybitmessage-dev-git/
Use the FreeBSD ports.