Let´s speak over the "Fractal" shader as example.
Each renderer will have a version with which he can work. Also one version for the Maya renderer, one for MentalRay.
To use this shader in Octane, we need also a new version which runs with Octane.
To explain it a little bit better.
Each shader is a little program which has some input ports, some outputs ports which are filled with color information.
This information is calculated from the renderer.
As example without to be correct, the Maya renderer reads in the color information from an image with position x and y.
MentalRay will also read the color information, but with y, x. You see, this doesn´t match.
As a sidenote, it isn´t possible to share data between different render engines. You can use either this renderer or that, but not this and that.
Ok, back how to create the "Fractal" shader in Octane.
The big problem is to know, how the shader calculate the fractal.
We can go different ways of calculation, but the result wouldn´t match the result from Maya or MentalRay.
And remember, the result we get is only an image with an x/y resolution which must be mapped to the surface.
It´s the same when you create a fractal in Photoshop and use it as texture in Octane.
Over the API we have only the possibility to fill in a texture with some colors.