The Tinderbox website uses an unfortunate choice of words to advertise how to upgrade. Instead of calling it an upgrade, it says "renew Tinderbox". In one sense, this is honest. You don't pay by the version number, but for a period of free updates. On the other hand, "renew" suggests that your license can expire. Of course, the website also contains a link that explains what they mean by renew, but by this point certain associations have already been awoken in the user. This problem is symptomatic of another issue: Tinderbox's documentation is nowhere near adequate. With this limitation, Tinderbox will always remain something of a niche product, and its updates will continue to be expensive.