Wikipedia starts by saying hypernext is freeware. When I went to download hac I noticed it mentioned trial limits and license key purchasing but didn't mention what the limits were beforehand. To find out I downloaded and installed it - found out that my programs would only run for 5 minutes without buying the license key - so I uninstalled hac. I'd guess the entire process took 5 minutes.
Moral of the story - tell people what the limitations are first, AND what the price of the key is BEFORE making the download it. Anything else comes across as entrapment.