As of this release, Magic is now 100% Open Source, and you no longer need to purchase a license to use it, not even to create close source code yourself. The main backend project is MIT licensed, which is the thing you'll probably want to modify yourself, as you create Magic applications - But the plugins are LGPL licensed, and the frontend dashboard is GPL licensed. This is to ensure improvements to Magic itself, stays open source.
For all practical concerns though, this means you can create any amount of closed source projects using Magic, but if you improve upon the actual project itself, you'll need to publish your improvements.