In the Joomla world, at least, there are a lot of companies who seem to be making money off of open source plugins. One common model is to allow downloads only

In the Joomla world, at least, there are a lot of companies who seem to be making money off of open source plugins. One common model is to allow downloads only after you've subscribed. (Yes, the plugins are typically GPL.) These usually come with automatic updates for a year for subscribers. Sometimes this can be bundled with "priority support" for 3x the price. And, of course, there's always the classic "upgrade to the pro version" pitch