Yes. See this question in the GPL FAQ:
"If a programming language interpreter is released under the GPL, does that mean programs written to be interpreted by it must be under GPL-compatible licenses?"
Despite the phrasing of the question, it actually includes the relevant answer:
---- However, when the interpreter is extended to provide âbindingsâ to other facilities (often, but not necessarily, libraries), the interpreted program is effectively linked to the facilities it uses through these bindings. So if these facilities are released under the GPL, the interpreted program that uses them must be released in a GPL-compatible way.
Another similar and very common case is to provide libraries with the interpreter which are themselves interpreted. For instance, Perl comes with many Perl modules, and a Java implementation comes with many Java classes. These libraries and the programs that call them are always dynamically linked together.
If you choose to use GPL'd Perl modules or Java classes in your program, you must release the program in a GPL-compatible way, regardless of the license used in the Perl or Java interpreter that the combined Perl or Java program will run on. ----
GSL is the "facilities" in this case. So the first paragraph means that the bindings themselves are under the GPL.
So the bindings are a "GPL'd module" in the second/third paragraph, and the third paragraph means that any program using the GSL bindings is also under the GPL.
Paolo