AIME is a C++ MUD engine with an OO design, designed to provide utmost flexibility for the designer to create complex worlds. It has a fully-functional builder port, online interpreted specials code, and a flexible levels/quest/profession track system to allow the game owners to set up any world they can imagine.
'App' is a preprocessor for C++ that accepts as input arbitrary C++ code that may contain embedded constructs for specifying algebraic data types and associated pattern matching operations, and produces as output the same code with all such constructs translated to normal C++. What app essentially does is provide for C++ pretty much the same capabilities that functional languages have regarding algebraic types. 'Applib' is the associated runtime library that supports the core run time requirements of the translated code, and which provides additional utilities (applib is covered by the LGPL).