NOT FOR REPLICATION is a property that can be applied to triggers, constraints and identity columns to prevent replicating them. You can set this property ON and OFF.
Here's a piece of T-SQL code to turn off NOT FOR REPLICATION for all tables:
EXEC sp_msforeachtable @command1 = '
declare @int int
set @int =object_id("?")
EXEC sys.sp_identitycolumnforreplication @int, 0'
(Addapted from http://blogs.msdn.com/b/repltalk/archive/2012/03/06/marking-identity-columns-as-not-for-replication-in-existing-publication.aspx)