As somebody who’s used OIDN once or twice before I can’t really see how it would be useful as a Natron plugin. Denoising CG is typically something that is done as a post-process job applied to already rendered frames on the farm, not in the comp software. It also comes with massive overhead (compared to other effects anyways, it’s not that slow) and should probably be done before your comp work anyhow.
In any case if you need to use it you can find downloads here.