It uses ImageMagick to do it's dirty work and features thumbnail and screen-resolution autosizing, autorotation based on EXIF data (provided your camera supports it) and Cheetah templating for generating pages.
The albums generated are completely static, reducing web server load (when it was originally written, my server was a 166MHz pentium II, so on-the-fly resizing of 3 MPixel photos was not an option :-)
Source is not generally available yet, sorry.