Indeed, the GPL says so explicitly. Quote: "Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted"
That is, you do *NOT* need to agree to the GPL in order to use the software, or indeed to do anything permitted under copyright-law. The GPL in effect says: "You don't have to agree with any of this - but *if* you agree, you get a set of additional rights, including the right to distribute, copy and modify the software"