For large projects open source doesn't seem to a big problem for commercial purposes even though we don't know whether anyone has produced a new OS from linux codes and sold it.
We estimate it didn't happen cos if it had happened ,we would have heard about a new OS running similar to linux and we would have suspected.. So noone dare such a thing I think..
On the other hand project written in php aren't that well-known. So if you write some code in Turkey, anyone in America can reuse it for own purposes and it is impossible you hear about it unless it becase a famous software..
Got it ?