The Rossum Project  
   An Open Source robotics project that aims to develop standardized simulators, control software, and APIs for mobile robotics applications. All code is Free Software licensed under the GNU GPL.
   http://rossum.sourceforge.net/

Player/Stage  
   Player is a language and platform independent network server for robot control. Stage simulates a population mobile robots in a 2D environment. Both are Free Software written in C++ and licensed under GNU GPL.
   http://playerstage.sourceforge.net/

TeamBots  
   A collection of Java-based control and simulation programs for multiagent mobile robotics research developed at CMU and Georgia Tech. Full source code is included. Non-commercial use only.
   http://www-2.cs.cmu.edu/~trb/TeamBots/

MissionLab  
   Multiagent robotics mission specification and control software. Takes high-level military-style plans and executes them with teams of real or simulated robots. MissionLab is proprietary software buy may be used at no cost in some non-commercial cases.
   http://www.cc.gatech.edu/aimosaic/robot-lab/research/MissionLab/

The Orocos Project  
   The Open Robot Control Software Project aims to develop an architecture-independent component based framework for all aspects of robot control. Orocos is Free Software licensed under the GNU LGPL.
   http://www.orocos.org/