On the Bourbaki's attitude towards category theory, there are various references (check online Liliane Beaulieu's bibliography on Bourbaki), but the fundamental study is undoubtedly that of Ralf Krömer. A very very good paper, limited only by the non-availability of Bourbaki's archives for the sixties : KRÖMER, Ralf La « machine de Grothendieck » se fonde-t-elle seulement sur des vocables métamathématiques? Bourbaki et les catégories au cours des années cinquante, Revue d'histoire des mathématiques 12-1 (2006), pages 119-162 Thank you to Paul for remembering my talk at Amiens. It was certainly related to the subject and also relied on Bourbaki's archives, but dealt with an earlier "pre-categories" period. Only a 2 pages abstract is so far available (I might write down a longer version some day in sha'a l-lah) : AGERON, Pierre Autour d’Ehresmann : Bourbaki, Cavaillès, Lautman, Cahiers de topologie et de géométrie différentielle catégoriques XLVI-3, pages 165-166 (available online via NUMDAM)