Is there any way to stop Sound Forge grabbing exclusive access to my audio interface?
It stops Sonarworks Reference from working and kills audio currently playing elsewhere in my system.
Welcome to the Magix forums.
I'm going to assume you are using the ASIO driver for whichever audio interface you have? If so, it is one of the limitations of that driver model that it demands exclusive access to your sound device. Because that limitation is built in to the ASIO specification, there is, unfortunately, nothing you can do to change this behaviour.
One possible solution is to download and install the free ASIO4All driver and use that; with some careful setting up it can allow the use of multiple audio sources. (Please notice the words I have deliberately bolded; no-one can guarantee that you will be able to make it work.)
HTH
Jeff