Understanding 'Derived Works'

Ah.. nothing like reading a piece of entertaining and enlightening article in the morning. For all the lawsuits, FAQs about "…can I take open source and sell as proprietary.. ", all the many many open source licenses with different ifs-then-elses.. somebody too tired has a nice closing note that gives a clear view of what derived works is. (non-techies: dive to the paragrah beginning with "As I was politely asked…")