RDS licensing
Every incoming connection that lands on an RDS server must have a valid client access license (CAL). These licenses are available for purchase from any normal avenue through which you purchase your Windows Server licensing, so I cannot tell you the best place to go to get these licenses, only that you need them, and how they work. There are two types of RDS CAL, and we will describe both, but the reality is that almost every RDS farm in the world uses User CALs.
User CALs
User CALs are the normal way to go. As the name implies, every user who is connecting to your RDS farm needs to have a User CAL. These CALs are installed on your Remote Desktop Licensing server, which like inside our test lab might co-exist alongside some other RDS roles, and once licenses are installed the RDSH servers check in with the Remote Desktop License server to ensure there is sufficient licensing to allow the connection to happen.
User CAL limits are not restricted at a technical...