Previously, you could get PhysX on amd systems by having PhysX run on the cpu or on a secondary Nvidia graphics card. So use an AMD gpu as your main gpu, and then let maybe a Gtx 560 run as a PhysX card. But, Nvidia released a driver update a while ago that disabled PhysX when an AMD card was present in the system. So now it is not possible to run PhysX on an AMD card, but it is disabled to run PhysX on a system that includes an AMD card.
So what you're saying is that now on AMD systems PhsyX is disabled even when it is rendered on the CPU? Or something else? The last bit of your post confused me.
APEX is a multi-platform, scalable dynamics framework. Rather than providing a low-level API that requires a physics programmer, APEX creates an environment where artists can create complex, high-level, dynamic systems without any programming. - http://www.nvidia.com/object/apex.html
I think APEX is the platform for everything. The effect that you posted in that screenshot is just APEX turbulence.
APEX provides support for the following modules and is available on Xbox360, PS3, and PC:
On any system with an AMD graphics card, PhysX is disabled on the cpu and on any Graphics card in the system. Say your system is a 6700k with a R9 290x, with a Gtx 560 ti installed as a PhysX card. In the past, the Gtx 560 ti could be used as a PhysX card. The Nvidia driver now prevents this from happening since there is also an AMD graphics card in the system. If the system was just the 6700k and R9 290x, the Nvidia driver will not allow PhysX to run on the CPU because there is not an Nvidia card in the system. If the system was just the 6700k and 560 ti, the Nvidia driver would allow PhysX to be run on either the CPU or the GPU. But as soon as you put in the AMD card, it will not run.
some games allow for enabling physX/apex without nv card. Like Borderlands & Mafia 2; most of time games will detect that there is no NV GPU or AMD gpu and will force disable those options. If there aren't any built-in checks you can use those effects with no issue.