WordNet (r) 3.0 (2006):

nonrestrictive
    adj 1: not limiting the reference of a modified word or phrase;
           "the nonrestrictive clause in `I always buy his books,
           which have influenced me greatly,' refers to his books
           generally and adds an additional fact about them"

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "nonrestrictive":
   broad-minded, culpably negligent, derelict, freethinking,
   inadvertent, inattentive, laissez-faire, latitudinarian, lax,
   liberal, libertarian, libertine, loose, neglectful, neglecting,
   negligent, noninterfering, off-guard, open-minded,
   overly permissive, permissive, procrastinating, relaxed, remiss,
   scamping, skimping, slack, slighting, slurring, tolerant,
   unbigoted, uncircumspect, unguarded, unrigorous, unwary,
   unwatchful