It's not a full shader, it's example OSL code. You'll need to plug that OSL code into an OSL node in an Octane shader network. As I recall, it was the Lightwave version that I could just drop into C4D Octane. Also, the source .exr is defined by a path in the OSL node, not with an Image Texture node, at least in this implementation.
(edit) I went and re-downloaded the files to see what you are seeing. The jiWindowbox.zip file expands to a directory of .osl and .oso files. You want the jiWindowbox_LWOctane.osl file. Open it with your favorite text editor and copy/paste it into the OSL nodes Script Editor window. You'll also want the jiWindowBox_Examples.zip to have some .exr files to plug into the shader and as a template for building your own.
(edit 02) I decided to make a little quickie demo file for C4D users. This file uses one of Julius' (credited in the ReadMe) .exr files and the OSL code as written for Lightwave.
- sample windowbox 0SL scene for C4D/Octane Render
- (7.94 MiB) Downloaded 340 times
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