Please go to:
at large - definition of at large by the Free Online Dictionary, Thesaurus and Encyclopedia.
at large : 1. Not in confinement or captivity; at liberty
I think it is used figuratively in the passage above.
So...it might be used as something like...."freely", I imagine.
I'm not a native speaker of English, so please forgive me if I'm wrong.
Please wait for native speakers to respond.