To quote the client tutorial (page 6) :
All communication in the SGS is done by sending and receiving byte arrays. To a Java coder this may seem a somewhat old-fashioned way of doing things. The SGS, however, is a client-agnostic system. The SGS team intends to deliver client APIs for J2SE, J2ME, and C/C++. Other platforms may also be identified as later client targets by the SGS team or by the community.
While a few cross-language object systems exist, they are either platform-specific (for example, DCOM) or very complex, with serious overhead (for example, CORBA). The conclusion of the team was that it was best for the system to provide the common and efficient base of sending and receiving arrays of bytes, and to let specific applications build on top of that according to their needs.