Sun has made the book ONC+ Developer's Guide available on Internet.
Program Number Registration
To register a protocol specification, send a request by email to email@example.com, or write to: RPC Administrator Sun Microsystems 2550 Garcia Avenue Mountain View, CA 94043 Please include a compilable rpcgen ".x" file describing your protocol. You will be given a unique program number in return. The RPC program numbers and protocol specifications of standard RPC services can be found in the include files in /usr/include/rpcsvc. These services, however, constitute only a small subset of those that have been registered.
ONC RPC for Unix/Linux
ONC RPC is part of the standard library for Unix/Linux. The full source code is available from the Free-BSD and Linux source code archives. Look for the rpc directory.
Man pages are aviailable from Sun. Look for the svc_* clnt_* auth_* rpc_* and xdr_* pages.
ONC RPC for windows NT
Martin F. Gergeleit has made a port of ONC RPC to Windows NT. The source code is freely available(?).
ACPLT/KS is a new C++ framework built on top of the RPC protocol, replacing the old fashion "C" interface to RPC. It's desinged for process control, and is available with source code here