I think this would be a good candidate for the ddf-libs repo if the interface does not cause an issue.  

I would expect the project on the ddf-libs side to have a maven dependency on a released version of the platform.  Since the interface has never changed, we should not have to update the platform version.  The platform dependency's scope would be set to provided.  Bundle that embed the configuration utils jar would need to then OSGi import the platform configuration API package.  

I am not 100% sure if that will all work but I think it is worth investigating first.  The ddf-libs repo will not be very useful if we have to exclude all utility code that requires an interface from one of the applications since I think that will be a common use case.