Welcome to 1912WebWorks!
QP5 is a free open source web engine that uses PHP and MySQL to build awesome websites. Out of the box it can do multiple blogs, handle multiple users, and multiple languages.
Towards the end of 2003 I started playing with different blog engines and decided wordpress was not for me because the code sucks. It looks pretty, but on the inside it was crap. b2evolution looked complicated but was really good on the inside, and was the beginning of "multi multi multi" straight out of the box. In early January of '04 I started using b2evolution for my websites. Unfortunately the primary developer decided using the core software to promote traffic (and eventually business) was acceptable. Links back to the source were *everywhere* and couldn't be removed without a lot of hard work.
Thus, towards the end of 2009, a small group of b2evolution users created Quam Plures, which is the source of this software package. We worked hard to undo most of the faults in b2evolution, and improve the software from a user's perspective. Worked out pretty good, except for one problem: when no one is in charge decisions about what next weren't getting made in a timely fashion. I still participate in Quam Plures development, and ensure that you can upgrade from there to here, but I decided to do my own thing so I could make changes I needed for my clients.