This was recently sent to me by a kind soul and I have confirmation that it works.
If anyone knows another way to get this library (other than signing up as a developer at Nvidia) please leave in comments.
Latest update (13.6) enables them in Windows only so I found out that you need to upgrade two files to make it work on OSX.
You can do it after copying two files from NVIDIA Optix SDK
to AE folder:
/Applications/Adobe After Effects CC 2015/Adobe After Effects CC 2015.app/Contents/Frameworks
These are the files that need to be replaced: