The DrQueue Open Source rendering framework offers you the best features you'll find on any other privative product of its class, plus many that not are not only present but due to their restrictive licensing policies will hardly ever be, if at all.
DrQueue is Open Source licensed under the GPL.
Python integration offers the possibility to write your own python tools in a few lines of codes.
Most importantly, being Python the scripting language of choice for both the Open Source and the closed tools like Maya or XSI, having python scripting capabilities will let you seamlessly integrate it with your existing toolset.
DrQueue offers you Free Software as in "Freedom".
Current versions of DrQueue, due to heavy planned modifications and merges, should be considered Beta versions. Please refer to our commercial support services for more information if you feel in the need for professional support.