I’ve mentioned before that I liked what the Cape Town Commitment had to say about contextualization. In particular, it has defined “insider movements” in a way that is very helpful as you will see below.

“So called ‘insider movements’ are to be found within several religions. These are groups of people who are now following Jesus as their God and Saviour. They meet together in small groups for fellowship, teaching, worship and prayer centred around Jesus and the Bible while continuing to live socially and culturally within their birth communities, including some elements of its religious observance.”

A couple important notes on that:

http://codylorance.blogspot.com/2011/05/response-to-james-white-on-insider.html