It uses the Ubuntu Linux Live CD as a base, and then allows customization of boot screens (usplash), gnome settings, and software (you can also use the chroot environment to make other changes before creating the live cd).
Reconstructor does not create separate distros. It keeps the solid Ubuntu foundation, and just allows for customization. For example, create a custom Live CD with blender, inkscape, etc. included for a friend in graphics, or simply use reconstructor to re-brand your environment (wallpaper, fonts).
Reconstructor is written in python and is licensed under the GNU General Public License (GPL)