The part of the sentence which is a nonrestrictive clause is 'which is free for full-time faculty.'
The nonrestrictive clause is the adjective clause which provides the meaning of the word whose meaning is already clear from the sentence. They begin with the word 'which' and ends with a comma and are removable. They provide additional information about the word. In the above sentence, the nonrestrictive clause is 'which is free for full-time faculty' which is giving an additional information about the 'cafeteria.'