Linden Lab sees a strong connection between Second Life Grid and virtual world open source code. We have always been a strong advocate of the use of open standards and the advantages of using open source products. Linden Lab relies on open standards and open source implementations when appropriate and available, though there are cases where we've relied on proprietary technologies or code. As evidence of that connection and belief, we provide our virtual world viewer as open source code for use in Second Life.
If you're interested in joining the open source viewer community, then join our mailing list, to identify and report bugs, or get the source to compile a viewer on your own.