I am wondering if there is a positive, formal counterpart to the slang "No strings attached" to describe, for example, a parent's unquestioned devotion to their children, or the virtue of someone's "a friend in need is a friend in deed", help first, question later mentality.
I think the word you are looking for is altruism
Pronunciation: Brit. /ˈaltrʊɪz(ə)m/ , U.S. /ˈæltrəˌwɪzəm/ , /ˈælˌtruˌɪzəm/
1. Disinterested or selfless concern for the well-being of others, esp. as a principle of action. Opposed to selfishness, egoism, or (in early use) egotism.
Philanthropist might be an alternative to altruism already suggested –
From Oxford English Dictionary (OED) –
A benefactor of humankind; one who behaves benevolently towards others; a practitioner of philanthropy.
You might want to consider altruism, ‘Disinterested or selfless concern for the well-being of others’ in the OED’s definition.