After seeing the following question one of my problems came in mind: I want to couple two different scripts in two different languages.
I found a solution for that, and I copied that solution. Unfortunately the same author uses this code for a script which he put under the GPL, but he did not mention the GPL in his example.
Can I use the connection (pipe-construction) in a non-free script, even if the script he uses this code is under the GPL?
I want to combine python and ruby, and I used the code from this page. Later I found out that he wrote a script licensed under the GPL using the same technique.