zith's opinion is perfectly clear and valid, and your attempt to nickpick it to death is unbecoming.
open source exists to encourage derivative works, zitheral does not want derivatives of his work.
accepting programming as a creative endeavour, his rational is easy to understand, and honestly made perfectly clear in his post.
creating a mod makes real your own personal vision, much like painting a picture or writing a song. maybe you want mona lisa with a butterfly in her hair, but da vinci didn't, and honestly I don't see a problem with allowing people to retain control of their work to ensure it stays true to their original intentions.
if you want to see mona lisa with butterfly, or mona lisa with flower, or mona lisa with bottle of wine, paint your own