Earlier this year I attended a 7710 (now 7750 SRc-12) core functions course. During that course, nearly all interaction (console) was done with simulators. Looking in the training datacenter, the majority of SR nodes were all simulators. So, they definitely exist and run as an application on a PC.
I too asked if I could obtain a copy of the simulator and was told they were for ALU internal use only, and could not be rented/purchased, etc. (security is very tight, I was told)
Maybe with additional customer interest, ALU would develop a customer-available application.