If you purchase a serial number for FeedDemon, that serial number will continue to work for all minor updates, but there will be an upgrade cost for the next major version.
For example, if you purchased a serial number for FeedDemon 3, that serial number worked in all 3.x versions, but it no longer worked in FeedDemon 4. Although FeedDemon 4 isn't a free upgrade, the cost of upgrading is very reasonable.
