Board Thread:Naruto Discussions/@comment-24847491-20140921145042/@comment-1512913-20140922124139

Actually, calling the natural energy passive absorption "sage transformation" is wrong, sage transformation is the result, not the kekkei genkai, but that's for another time.

As you say, Kabuto is a Sage Mode user through Jugo's powers, so by extension should be Jugo himself.