ThinClient Licensing

We need advisory on ThinClient licensing for the below scenario.

Scenario:

We need to install Linux based thin client set up at our premises and following services will be installed on server:

1. Remote Desktop Gateway
2. Remote Desktop Licensing
3. Remote Desktop Session Host

So what will be our licensing needs whether we required an RDS CAL with Windows Server CAL only or we need VDA rights (for thin client) with RDS & Win Svr CAL ?

Since we also have N numbers of RDS CAL available and installed in Citrix Server to access the Application. So, can we use these CAL and install them in “Remote Desktop Licensing Server” simultaneously.