GNU Robbo ver: 0.68.rc4d.1
Author: GNU Robbo team
Website: gnurobbo.sourceforge.net
Description:
This is an Atari Robbo (originally by Janusz Pelc) clone with over a thousand levels. GNU Robbo is also compatible with two clones of Robbo, such as Alex, Robbo Millenium. To get Robbo Millenium levelset, you need to buy a copy at LK Avalon, and then use a converter to import levels into GNU Robbo. The converter is located in GNU Robbo's svn repository. This is unofficial release, but a lot of levels were tested by Bradley Knockel, all of tre robbo can now be beaten. Yet it contains many untested yet levels, so most probably there are some levels impossible to be finished. You could fix them with level designer, which is built in.

Licenses:
GPLv2 - source code