It seems to me that in open source model open source is a compound modifier of model some would hyphenate open source to be clear Searching for source model seems to always find it preceded by an adjective open participle closed or noun community compounding with source One instance where source model is clearly atomic is here where source model is used to mean gcc s internal model of the source code Maybe what we re really talking about is license for use of object code and license for use of source code Regards