The world of software licensing is, to be honest, a fairly dull one. Lots of reading and interpreting of legal documents, analysis of the meaning of terms, and negotiation with copyright holders.
You would be forgiven for thinking, perhaps, that discussing what is or is not a “derived work” under copyright law (a fairly key point with regard to the GPL, for example) is not the most exciting way to spend your evenings.
However, things can liven up occasionally, as they did last week on debian-legal, where a contributor who was frustrated at going around in circles on an argument over the use of the GPLed Kaffe VM to run the CPLed Eclipse IDE used a fairly graphical but memorable analogy to explain what a “derived work” actually is. I can’t say I’ll ever be using it myself, but it’s an amusing read.