Draw.io -- Is there non-minified source?

The minified and non-minified (NM) sources are both in the project. The NM sources mostly live in the diagramly folder (the old name for draw.io) and the GraphEditor folder.

If you look in the build file, you can see which sources go into which *.min.js files.

The GraphEditor source serve as the base stack under draw.io. It used to be maintained as a cut-down editor, just not any longer.