Yes, however, GitHub's Terms of Service section F.1. (http://help.github.com/terms-of-service/#f_copyright_and_content_ownership http://help.github.com/terms-of

Yes, however, GitHub's Terms of Service section F.1. (http://help.github.com/terms-of-service/#f_copyright_and_content_ownership http://help.github.com/terms-of-service/#f_copyright_and_con...) specifies "By setting your repositories to be viewed publicly, you agree to allow others to view and fork your repositories." I suppose you could write a license that allows others to view and copy your code, but not make any modifications, as fork doesn't seem to be defined to include modification.