The patch does recompile or replace the entire termsrv.dll . Instead, it performs a binary hex edit – modifying specific machine code instructions that control the session count logic.
The is a manual modification of the Terminal Services library to bypass the default limit on concurrent Remote Desktop Protocol (RDP) sessions. While Windows Server 2019 allows two simultaneous administrative sessions by default, users often seek this patch to enable multiple sessions for more than two users without purchasing expensive Remote Desktop Services (RDS) Client Access Licenses (CALs). Understanding termsrv.dll windows server 2019 termsrv.dll patch
For home labs or non-commercial testing, the patch is a gray area but rarely enforced. For any revenue-generating or client-facing environment, and use official RDS licensing. The patch does recompile or replace the entire termsrv