aismann
In general, if users utilize a tool/library/SDK that integrates a Spine runtime to create their own game or software, they are required to obtain a license.
Here is an excerpt from the runtime license agreement:
Otherwise, it is permitted to integrate the Spine Runtimes into software or otherwise create derivative works of the Spine Runtimes (collectively, “Products”), provided that each user of the Products must obtain their own Spine Editor license, and redistribution of the Products in any form must include this license and copyright notice.
You are creating a “scene editor,” which can be considered a tool. The tool itself does not require a license, but you must include the Spine Runtimes License Agreement and clearly state that end users must obtain their own Spine Editor license.
However, if you use your tool to create a cocos2d-x game, then you will need a license.