The developing agents CD3 and CD4 can be purchased commercially. CD6 cannot be purchased except through Kodak or an associated company AFAIK. The big problem would be getting the couplers. They are very rare and only made by/for Kodak.
See the patent, # posted elsewhere by Bent and Mowrey for Kodachrome.
And, BTW, Kodak vacated the patent, thereby donating it to the public.