Oculus didn't mention the removal of the Rift DRM setup in its change notes for the runtime update (via Ars Technica). However, the developer behind the third-party "Revive" software app that has been trying to get Rift exclusives on the HTC Vive noticed the change.
I've only just tested this and I'm still in disbelief, but it looks like Oculus removed the headset check from the DRM in Oculus Runtime 1.5. As such I've reverted the DRM patch and removed all binaries from previous releases that contained the patch.
So far, Oculus has not officially commented on this apparent change in policy for its games. Ars Technica adds:
So long as users are running official Oculus software, and its always-on runtimes, Revive patch users can expect to see their whole Oculus gaming collection selectable with the HTC Vive's handheld wands. The only thing that remains to be seen is how Oculus reads the motion-tracked data from its upcoming handheld controller system, the Oculus Touch, and whether Revive will be able to do the same thing for the HTC Vive's wands once Touch-compatible games launch later this year.