Zomplog was an open source php weblog-system that was widely used between 2004 and 2008.
For research purposes you can still download the old version here:
Download the latest version of Zomplog (version 3.9)
Download the Zomplog Extension Pack (including 16 languages, 19 plugins and 5 themes!).
Need a weblog system?
Try BlogBird, my new weblog system.