Copy the original, unmodified termsrv.dll file to a secure backup directory (e.g., C:\Backup\termsrv.dll.bak ). Step-by-Step Guide to Patching termsrv.dll
The so-called "termsrv.dll patch" is an unofficial modification to this file. Its purpose is to , allowing multiple users to connect simultaneously via RDP without purchasing and installing Remote Desktop Session Host (RDSH) CALs (Client Access Licenses). termsrv.dll patch windows server 2016