Actually mercs are now built into the code, just need to activate them via sql queries to enable them as they are not enabled in the deafult peq db, bots, in reference to EQEMU, are an optional build, when you run cmake, there is an option to build "bots", but, unfortunately the process of building "bots" is not enough to enable them.
So they are, in eqemu terms two different but similar entities..The bots and mercs function almost exactly alike, with the exception the bots can be used to build whole raids, but they act almost like mercs, as they have similar code. But with bots you can give them gear as you acquire it...
I wrote about this a while back, in this thread:
http://www.eqemulator.org/forums/showthread.php?t=37295