Second Life publisher Linden Lab has released virtual world's viewer as open source software, and intends to do the same with the server software that runs the virtual world itself. Linden Lab released the viewer software under the open source General Public Licence (GPL), which allows anyone to view, change and distribute source code, but requires anyone who distributes modified software to make the changes available as well. Linden Lab will require programmers to sign a contributor agreement which gives Linden Lab joint ownership of the software; Linden Lab will also maintain control of an official version of the viewer software.
This is a big step in the games industry, as most large game companies prefer to keep their code proprietary. However, Linden Lab believes that Second Life lends itself to an open source approach, and also believes that it still has significant income potential even if software is open source.