WordWeb may be freely used only by people who meet the conditions below.
Global greenhouse gas emissions are currently around 1 tonne per person per year, and need to be greatly reduced to avoid catastrophic warming this century. Most computer users are responsible for far more emissions than is sustainable. For example one medium distance return flight can be warming-equivalent to over 1 tonne of emissions: more than an average person should be emitting in an entire year. A typical SUV causes about twice as much warming per mile as a typical normal European car: 10,000 miles of travel in an SUV is responsible for about 5 tonnes of emissions. Offsetting emissions is no substitute for direct cuts.
You may use the program free of charge indefinitely only if
* You take at most 4 flights (2 return flights) in any 12 month period
* AND you do not own or regularly drive an SUV (sports utility vehicle).
Surely not effective on its own as a way of making a difference, but it is a curious and interesting extension of the copyleft mechanisms developed in the free software movement: to stipulate legal/moral obligations to use a particular piece of code, but extending those obligations beyond the normal provisions of software licenses.
I don’t know how legal such things are, but it’s very very interesting, and very creative.