WordWeb is a dictionary and word finder. Its one of those very useful freewares. When you want to install the Word Web Pro freeware version then you have to agree for a license ( of course everybody has that I agree checkbox). Here comes the interesting part. To get a free version you must agree to the following

Pretty cool. They have an explanation for this kind of licensing

Various people have questioned the WordWeb 5 licensing terms. It is true that targetting flights and SUVs is a very crude measure; many people’s CO2 emissions come mostly from their home due to inefficient heating, insulation or air conditioning. However the licence is designed to be easy to understand, and sufficiently simple that people will know immediately whether or not they satisfy it. If you break the licence you are certainly responsible for more emissions per person than are sustainable, and you can certainly afford to buy the Pro version. The licence is not telling you what to do: that is up to you, but if you don’t satisfy the licence you need to pay.