New video from Boko Haram, via the BBC, shows about 120 of the kidnapped Christian girls dressed in Islamic garb -- chadors -- and reciting verses from the Qur'an. In the 2nd video, the Boko Haram leader says that the girls have been "liberated" by becoming Muslim. “These girls, these girls you occupy yourselves with… we have indeed liberated them. We have indeed liberated them. Do you know we have liberated them? These girls have become Muslims."
https://www.youtube.com/...
https://www.youtube.com/...
He also says, “We will never release them (the girls) until after you release our brethren. Here I mean those girls who have not submitted (converted to Islam).” The implication is that some of the Christian girls are refusing to convert, and so those are the ones that will be held indefinitely -- but there's no offer to let the converted girls go, either.
Boko Haram is making it clear what they had in mind when they named themselves the Congregation of the People of Tradition for Proselytism and Jihad* -- their official name; Boko Haram is a nickname. One thing we can say for them is that they're pretty open about their agenda.
*Jamā'at ahl as-sunnah li-da'wa wa-l-jihād (جماعة أهل السنة للدعوة والجهاد)