EXP is a pack of new entites for use by mappers in Far Cry. They are primarily made for use in SP maps. Many can probably be used in MP maps too but it is untested so far. You can use them for free in any map or mod provided it is released for free and I get credit for it. Note that this beta requires EXP 2.0 (Entity Xpansion Pack v2.0) to be installed!