The open source content management system has a strong history and a firm community. Recently, version 5.7 was released, and then swiftly upgraded with a further two minor updates.
From amongst these latest updates to the marketplace though, merchants offering add-ons and themes within the Concrete5 marketplace have enhanced capabilities. For example, developers can sell 30 day support windows and offer upgrades from one add-on/theme to another.
Here's a video explaining all the new Concrete5 Marketplace upgrades: