Reading TSplus's Benefits overview they claim that there is No requirement for Terminal Service CALs. No need for Terminal Service (Remote Desktop Services) license manager. However one of the posts indicates that M$ still requires CALs.
This is from the License Agreement of TSplus:
For Microsoft and non-Microsoft applications, you should consult the license agreement accompanying the applicable software or contact the applicable licensor to determine whether use of the software with Remote Desktop or Remote Assistance is permitted without an additional license.
So they give you their opinion on their web site, but in the legal papers they make you responsible for checking their claims with Microsoft. When you do, you find this in the Windows 2012 R2 EULA
CAL for each user or device that (...) accesses the server software to host a graphical user interface (using (...) other technology).
or this in the Windows 10 EULA
you may not: (...) make the software available for simultaneous use by multiple users over a network