Opensource ZigBee stack?

I was planning on getting the Telegesis ETRX2USB  and wanted to know if there are any open source (or shareware) open source ZigBee stacks that I can use with that?

I also wanted to know if there is any opensource (or not too expensive), network management or network analyser for a ZigBee network? Essentially I want to be able to programatically view network and node information on the ZigBee network (e.g. S/N ratio, signal strength, etc.) - something similar to Ember's Insight Desktop which shows the details  I am interested in. I could not find anything specific and would be interested in getting ideas.