What do you think the 'P' in GPL stands for?
Regardless:
1) You don't need a license to look at things. Copyrights reserve very specific rights: Reproduction, creating derivative works, distribution (limited to first sale), performance, display, and in some cases, transmission
2) And data can't be copyrighted.
US IP law is based on a clause in the US Constitution, and is fundamentally bounded in reach.