Munki

Thanks to OCSNG, I just came across Munki. From their description:

Munki is a set of tools that, used together with a webserver-based repository of packages and package metadata, can be used by OS X administrators to manage software installs (and in many cases removals) on OS X client machines.

Munki can install software packaged in the Apple package format, and also supports Adobe CS3/CS4/CS5/CS6 Enterprise Deployment "packages", and drag-and-drop disk images as installer sources.

Additionally, Munki can be configured to install Apple Software Updates, either from Apple's server, or yours.

All that and it's Apache-licensed, too.