Is DRM a standalone application or is it a setup file?
If DRM is a setup file (e.g. EXE, MSI), here is how you can proceed:
You can have two project:
1. APP1 + DRM
2. APP2 + DRM
where DRM can be installed as a feature based prerequisite, for instance.
In addition to that, I would also set some installation conditions for the DRM setup file. For instance, if it is installed in the first setup (APP1 + DRM), it shouldn't be installed in the second one as well (APP2 + DRM).
This can be done from "Prerequisites"
page --> your prerequisite --> "Install Conditions"
Hope this helps.