On the Various Flavors of Open Source Licences...

Icebox asks: "With the increasing number of for-profit software vendors releasing their products as open source I am beginning to concern myself more and more with licensing. Many of these vendors choose to write their own licenses rather than release under something that is already out there. After following the Qt announcement and reading statements like "the Qt license was incompatible with the GPL" (from RMS and others) I would like to research the subject on my own. This question came up on Slashdot before, but that was prior to the flood of new licenses. I even found this which seems like a good analysis of what should be the aim of OSS licenses. Does anyone know of a good source for legal precedents for any of the open licenses? (if there are any) How about a comparison of the various licenses from a legal perspective? This would seem to be a necessity if anyone plans to combine code from GPL, IPL, LGPL, BSD, NPL, etc.."