What's the meaning of "a non-normative document"?
Does "non-normative" mean "casual"?
What's the significant difference between a normative document and a non-normative one?
I typically see this in reference to standards and technical documents. A normative definition or statement is one that should be taken as authoritative or imperative (i.e., a should or a must), while a non-normative one is one that bears no such restriction.
Synonyms for normative would include prescriptive, so synonyms of non-normative could range from descriptive to declarative to informal or casual, depending on context.
Basically, it means "informal" or "nonstandard", as from the Free Online Dictionary: