Valedictory validates dicts. It operates in a manner superficially similar to Django forms, but is tuned for use in API validation, and other situations where you are receiving JSON as opposed to key-value POST form data. It takes in a dict of data (probably obtained from a JSON POST request), and validates that data against some criteria.
Input data can be typed, unlike regular Django forms, and validators can be nested, again unlike Django forms.
Additionally, Validator themselves are stateless once constructed. You can reuse the same Validator instance to validate input data multiple times, from multiple sources.
Django is not a requirement. It is just useful as a comparison.