Open source software at centralized servers?
Does anyone know of examples of open source software projects which are developing software that is run on large centralized servers? I can think of one example off the top of my head – Second Life – but can’t think of any others.
(I am, of course, asking for a reason – I’m interested in whether open source might be a viable development model for tools for scientific collaboration and publication.)
My impression at the moment is that there are few centralized web services which are open source. I can think of a couple of natural reasons why this might be the case.
First are security issues. In any software development one needs to be sure the programmers are honest, and not slipping back doors into the code, or making unethical use of the database. This is potentially harder to control in an open source software project.
Second, although the software may in some sense be owned by the wider community, it does not necessarily follow that the server is owned by the wider community. The group that owns the servers has a much greater incentive to contribute, and other people less so, which lessens the advantages to be had by open sourcing the project.
Are there any reasons I’m missing? Centralized services other than Second Life which are open source?