License: GNU General Public License, according to http://www.winpenpack.com/main/download.php?view.93, but I could not find confirmation of this at the original author's website
Description: LeoCAD is a CAD program that uses bricks similar to those found in many toys (but they don't represent any particular brand). Currently it has a library of more than 1000 different pieces, and with the recent LDraw parts update (see http://www.philohome.com/leoupd/leoupd.htm) this number has risen well above that.
Other: I don't think this app has any dependencies. I'm not sure whether it writes anything to the registry (probably does), but it does create some extra subfolders under My Documents. Development has apparently stalled, or is delayed in any case (no more development activity since 05/2009)
Thank you for considering!