Last week I had a coffee with guy who calls himself a "born again Muslim". His mother was the first in his Indonesian village to follow Isa (Jesus) and she met secretly for about 3 years with other Jesus followers to pray for their families. Her son soon had an encounter with Isa and he decided to follow him. He was a new person. His guilt was taken away. He was clean. His life was changed. His friends noticed.
Soon most of the viilage also believed in Isa.
He decided not to change the religious affiliation on his identity card. By leaving it as "Islam", rather than changing it to "Christian" it was not illegal for him to talk about Isa with his friends. And by not starting a Western style church, there was nothing for the authorities to burn down, which is a common occurrence in some of these islands.
Many Indonesians who experience a religious encounter like this do not change their ID religious affiliation until all their friends have learned about Jesus. Some change it at marriage. Some will wait for their whole family to follow Isa before they make a group (oikos) decision to change it, if they decide to change it at all.
My friend later met a Christian girl and fell in love. Since you cannot marry outside your religion in Indonesia, he chose to change his identity card to "Christian". But he still refers to himself as a "born again Muslim" who follows Isa
BTW, this guy had never heard of the term "insider movement". This is not an intellectual missiological issue as it is in the West but rather something more personal, more practical. There are millions of people like him around the world and this movement has become quite controversial in mission circles for nearly 20 years. If you would like me to blog more about it, let me know.
Related on TSK: Emerging Muslim Followers of Jesus