http://xlloop.sourceforge.net/

XLLoop is a framework for implementing a warehouse of excel functions
out of process and has the following features:

   * Fast binary protocol (overhead approx. one 10th of a
millisecond).
   * Extensible server framework.
   * Reflection-based function adapter for extremely quick deployment
of java methods.
   * Bean scripting framework adapter so functions can be written in
any BSF-supported language.
   * Functions can be dynamically added to excel without restart.

XLLoop consists of two main components:

   * An excel addin implementation (xll written in c++).
   * A server and framework (written in java).

The addin and server communicate via a simple socket-based protocol,
sending and receiving (binary) serialised xl objects (called xlopers).

XLLoop is licensed under the Common Public License (CPL).