How to use .make files? (No core project specified)

I'm trying to use one of the .make files, but I've the following issues:

$ drush make gplib.make 
Make new site in the current directory? (y/n): y
Beginning to build gplib.make.                                                                                                                                                                                                     [ok]
No core project specified.                                                                                      

$ drush make --yes grammar_parser_lib.make 
Make new site in the current directory? (y/n): y
Beginning to build grammar_parser_lib.make.                                                                                                                                                                                        [ok]
No core project specified.                                                                                    

Any suggestions?

I've Drush Version : 6.1.0