
   It is indeed different usage of the word Muslim . In Bosnia , it is more or
less used as an ethnic term not as religious one . There are people in Bosnia
who refer to themselves as "Christian Bosnian Muslims" if you can make sense
of that . Bosnian Serbs and Bosnian Muslims have the same language. 
Bosnian Muslims are mainly beleivers of Islam. I got this from Bosnian Muslim
friend of mine who goes to University of Texas in Austin.