"Sirikata is an BSD licensed open source platform for virtual worlds. We aim to provide a set of libraries and protocols which can be used to deploy a virtual world, as well as fully featured sample implementations of services for hosting and deploying these worlds."
When I looked around on their site and subcribed to one of their lists, I recognized a name among the subscribers - Kyle Machulis of teledildonic fame and ex-LL-employee, who I had met 2007 at a dorkbotSF at San Francisco's Porn Palace where he presented some of his dildonic equipment, while I was there helping present the Mind Reading Martini Maker.
Says Kyle about Sirikata: "Turns out the sortof-project manager of sirikata was an ex-coworker from Linden, and contacted me about it. I've pretty much just been lurking on the list, haven't had much time to interact, but I've got high hopes for the platform, as there were lots of things I wanted to do at Linden/SL that never happened."
All I want to add is that listening to artist Chris Platz in that video above makes me feel like I spend my days playing in the sandbox. .. Wait, that can be a good thing actually!