[Derision]

Looks like an old header file that isn't used any more. The one that is used is

zone/client.cpp

int16 Client::MaxSkill(SkillType skillid, int16 class_, int16 level) const {
        return(database.GetSkillCap(class_, skillid, level));
}

Delete zone/maxskill.h and everything still compiles, ergo it isn't used anymore.