A great site I have found that explains messianic judism is
www.lightofmashiach.org They have a very interesting and informative questions and answer section. The messianic congregations I know of are a mixture of Jews and Gentiles who accept Jesus/Yeshua as messiah but, follow the old holidays just have added the new testament fulfillments to the ceremonies. I do know that there are Jews in Israel who are called Messianics that do not believe in Yeshua as Messiah but, are very devote Jews and they think their messiah will be coming soon...for example many of the settlers over in Gaza (of course they were forced out awhile back by their own gov't) Maybe those are the Messianic that Livingston is talking about?