LibreCUDA is a project aimed at replacing the CUDA driver API to enable launching CUDA code on Nvidia GPUs without relying on the proprietary CUDA runtime. It achieves this by communicating directly with the hardware via ioctls, (specifically what Nvidia's open-gpu-kernel-modules refer to as the rmapi), as well as QMD, Nvidia's MMIO command queue structure. LibreCUDA is capable of uploading CUDA ELF binaries onto the GPU and launching them via the command queue.
Yeah that is often the issue.
It is rare a single company owns all the IP on code. So its common that companies are not releasing code because they cannot.