windows 2012 R2 remote desktop services -- active directory is a requirement , and a second RDS server should be able to use the first license server

windows 2003 TS and windows 2008 R2 RDS can work in workgroup mode.

but server 2012 / R2 requires active directory

yes, AD is required

also when I enabled RDS role the other day, the broke role got an error , in this case I need re-enable PS remoting

also add a 2nd RDS server, do it the low-tech way, dont have to configure the gateway, set itself as broker, point the license server to the 1st RDS which has the licensing role.