The license page is very clear on this: https://defold.com/license/

* You are free to commercialise any software created using Defold * You are free to commercialise any plugin, extension or tool created for use with Defold * You are free to modify Defold and you are not required to share the changes * You are free to distribute original or modified (derivative) versions of Defold * You are given a license to any patent that covers Defold

You can sell anything you want created with or related to Defold, but not package the engine+editor and sell those.