One of the clauses discussing exposing of the interface, which the CDK is certainly doing. Being Java, I see no way of restricting access to the Jumbo API:
(8) You are permitted to link Modified and Standard Versions with
other works, to embed the Package in a larger work of your own, or
to build stand-alone binary or bytecode versions of applications that
include the Package, and Distribute the result without restriction,
provided the result does not expose a direct interface to the Package.
Clarification must be sought with the Jumbo authors.