Are you in the USA? It's because Roget as a title isn't trademarked there so it's accepted as a name for any thesaurus. If you want the latest edition of the "

Are you in the USA? It's because Roget as a title isn't trademarked there so it's accepted as a name for any thesaurus. If you want the latest edition of the "real" Roget's, it's the one published by Longman.