I'm afraid this software is closed source. Why do you need it?
I will answer for them. Because by reusing the code of this editor, you can create a level editor that will be more convenient than the ugly Tiled.
You can check the code of rFXGen, rGuiStyler, rGuiIcons and rIconPacker, they are open source and all my tools use the same base template so the code structure is almost the same. rTexPacker just has specific code to package sprites but that's a few lines of code because it uses stb_rect_pack library.
This is rather impolite to the creator of Tiled.