You only need NVIDIA GPU drivers installed to run binaries that have OpenCL support. libOpenCL.so is included with the drivers.
In order to compile the applications you will also need OpenCL headers. Those may come from CUDA Toolkit, from a separate package (like opencl-headers
for Ubuntu), or you can just download them from the Khronos site (keep in mind that NVIDIA implements version 1.1 of OpenCL specification).