The Collaborative International Dictionary of English v.0.48:

Inoffensive \In"of*fen"sive\, a. [Pref. in- not + offensiue: cf.
   F. inoffensif.]
   1. Giving no offense, or provocation; causing no uneasiness,
      annoyance, or disturbance; as, an inoffensive man, answer,
      appearance.
      [1913 Webster]

   2. Harmless; doing no injury or mischief. --Dryden.
      [1913 Webster]

   3. Not obstructing; presenting no interruption or hindrance.
      [R.] --Milton.
      [1913 Webster]

            So have I seen a river gently glide
            In a smooth course, and inoffensive tide. --Addison.
      -- In"of*fen"sive*ly, adv. -- In"of*fen"sive*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

inoffensively
    adv 1: in a not unpleasantly offensive manner; "that wretched
           beast, the elephant, breathing inoffensively not a pace
           behind me" [ant: offensively]