I don't consider "sprang" to be a linking verb. For me "sprang open" is a phrasal verb.
Student or Learner
One meaning of the word "spring" as a verb is "to be released suddenly from a constrained position".
I've found one sentence to be the example: The door sprang open.
In this case, if "open" is adj,
1. Is "sprang" in this case a linking verb so "open" is adj?
2. Or, there is "to be" omitted. The door sprang (to be ) open.
Or, "open" is adv for the verb "sprang" ?
'Phrasal verbs are idiomatic expressions, combining verbs and prepositions .'── quoted from http://www.usingenglish.com/reference/phrasal-verbs/
Can 'verb + adjective' also be a phrasal verb?
I am not a teacher.
There is little point in being a purist when so many writers use the term 'phrasal verb' in so many different ways. Personally, I reserve special labels for combinations of a verb and preposition/adverb/particle in which the combined meaning of the two-word phrase cannot easily be inferred from the normal meaning of the two words individually. As 'spring' is used about objects that open or move quickly and with a lot of energy (http://www.macmillandictionary.com/d...rican/spring_2), the meaning of 'spring open' is transparent, and so it is not a phrasal verb for me.
For my personal views on multi-word verbs, verbs followed by a preposition, prepositional verbs, and phrasal verbs, see http://www.usingenglish.com/articles/phrasal-verbs-multiword-verbs.html
A great American grammarian seems to agree with you.
Dr. George Oliver Curme in his 1931 masterpiece A Grammar of the English Language (Volume II, page 37) gives this sentence:
""But, then, evening came, and the stars sprang alight." [He graciously gives credit for this sentence to one Sarah Gertrude Millin.]
He considers this to be an example of copula + adjective.
I am not greatly convinced that it is/was a copula verb. It strikes me as a lexical verb denoting the change, and rate of change, in the stars' appearance.