It was only a matter of time.
When Metaverse-in-a-teacup: Second Life recently went open source the obvious killer app was a local version of the Second Life "sim". A pocket version of a single Second Life island running on your servers (instead of Linden Labs') would enable safe world-building and could eventually make possible a decentralized grid of simulators mirroring and interchangeable with the existing web. Imagine it: a free 3D gamespace as media-rich as Second Life - as a virulent as blogs.
We've now got our first serious contender in Open Sim . And Second Life insider reports that it's also pretty easy to get started. Check it out, and consider lending your considerable talents to make the Metaverse a reality.