Mike,
You cannot run more than one instance of mgcld on a server at a time. You can combine the licenses files if they're using the same server ID, however. If they are using different yet valid server IDs, there is a slightly more complicated process you can follow to combine them under one daemon. See the following TechNote: https://supportnet.mentor.com/portal?do=reference.technote&id=MG76887
Guy