The "benefit" alluded to here was djb's secure codebase. As soon as your arrangement requires
[original codebase] + [random 3rd party codebase(s) tacked on], the security of the final
product becomes only as secure as the weaker of the two (or three or more) codebases. It
could even be argued that a product which incorporates all the required features into a single
codebase, if written by even moderately competent programmers, could be less risky than
merging multiple products into one.