Typically, when you read a particular software license, it usually says you have a 30-day trial period and you are required to purchase the software afterward. Recently, I read an article on the 10 Great Software Program You Can Get Gratis on TechNewsWord, and I was interested installing WordWeb 5.1.
Occasionally, I read the software license before I install it, or at least skim through it.
Here is the first paragraph of the license for WordWeb 5.1:
WordWeb free version may be used indefinitely only by people who take at most two commercial flights (not more than one return flight) in any 12 month period. People who fly more than this need to purchase the Pro version if they wish to continue to use it after a 30-day trial period.
The first time I read it, I asked myself did I click the correct hyperlink. After reading on the license, it turns out that the person who wrote this license concerns about the environment. He/she wants you be aware of how much greenhouse gas you produce each time you take the flight. I don't know how many user will take this seriously, but at least it get the message out.