There is a misunderstanding. Of course OSM is allowed to include information that can also be found in commercial maps. The difference is that you are not allowed to *copy* information from commercial maps or other sources that are protected by a copyright.
Also see the [beginner's guide about collecting data][1].
data][1] as well as the [Legal FAQ about contributing][2].
[1]: http://wiki.openstreetmap.org/wiki/Beginners_Guide_1.1http://wiki.openstreetmap.org/wiki/Beginners_Guide_1.1
[2]: http://wiki.openstreetmap.org/wiki/Legal_FAQ#2._Contributing