The practical way to install software on OpenMoko is with the Ipkg package manager, possibly via the graphical Application Manager. Naturally, you need to have obtained an OpenMoko system by other means initially.
In the shell, "ipkg install new-app" will download and install "new-app", "ipkg update" will update the list of available packages, and "ipkg upgrade" will download and install all packages that have a newer version available.
Precompiled ipk package files are available at least at:
Ipkg re-implements for embedded systems the Debian tools dpkg, apt, and apt-get. For example, it uses much less disk space for the package metadata.