For a CPU version,I find ispc to be a great language for graphics stuff, as it lets you easily take advantage of SSE/AVX/etc
To get wider usage, you'd either need a fast CPU version, or alternatively a HLSL (compute shader) and/or OpenCL version (more game developers use HLSL than OpenCL, but in other industries, architectural visualization, etc, it might be the opposite).
You could potentially start an open-source project and see if you can find other interested people to help with these ports.
Alternatively, if you do the ports yourself (and some optimization work), you could end up with a potential middleware product.
What kind of tools do you have for importing content? Do you have some kind of pipeline for pre-converting polygonal data into voxel data?
I just made a game for a game-jam using ray-marching in a pixel shader, which is quite slow, so I decided to go with an early 90's graphics style and present the game in 320 x 200 pixels
Indie game fans seem to love retro graphics, so if you want to make a game with your renderer maybe you could go that direction, where the performance of your ray-caster would be adequate.