We also have a DR SAS environment. In our case it is hosted in a separate data centre, 800 km from the Production one, and is run on a warm standby basis. That is it is switched on, but no SAS processes are running. We have an overnight replication process which copies Prod SAS metadata content and SAS data to DR.
The Production and DR SAS environments share the same network alias (CNAME), so only one environment can be running at any one time. IT just switch the IP addresses to move from Prod to DR or vice versa. Under the terms of our licence agreement we only pay for one SAS environment and the same SAS licence runs on both Prod and DR. When running on DR, we get warnings that SAS is not licensed to run on this CPU but everything still works. We don't need a temporary licence.
Whether you do or do not need a temporary licence for your DR environment would depend on the terms and conditions of your SAS licence agreement.