One year from first registering, the right to use new major and minor versions Tinderbox ceases unless you purchase an upgrade licence. An 'upgrade' licence renews free use of new releases for a further year, i.e. for 12 months from the issue date of upgrade licence. If your current cover has not quite expired the new period is added to the end of the existing one.
Therefore, those wanting continued full access to all new releases should purchase upgrade licences on a yearly basis, but this is not a requirement for continued use.
An upgrade licence allows the user to move from any past Tinderbox version to the latest release. As the licence code controls access to all releases, the terms upgrade and update can be regarded as interchangeable.
If a user is outside the free update cover period, new releases may still be downloaded and tried, though use a separate install location and note the the newer version will run in demo mode.
The user is not prompted for upgrades, but it is possible to check the number of remaining months access to new versions and the current licence code via the Register tab of Preferences.
It is not a requirement that upgrades be purchased before expiry of the current free update period. This offers flexibility, especially for those with limited budget for upgrades. Thus it is allowable for the original or a renewal upgrade licence's free upgrade period to elapse and then purchase a new upgrade at some later date. Simply register the upgrade, download the current version and carry on installing new versions for a further year.
Put another way, an existing user can run any version of Tinderbox. If the release date of that version post-dates the end of their free upgrade access, the app will run in demo mode. If within the current access period, the app will run normally; the upgrade licence ensures continued unlocking of new releases.