Yes, CONTRIBUTOR is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, N 1, T 1, R 1, I 1, B 3, U 1, T 1, O 1, R 1.

Is it a valid word?

CONTRIBUTOR is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

someone who contributes (or promises to contribute) a sum of money
a writer whose work is published in a newspaper or magazine or as part of a book