Copernic Desktop Search v1.5 Beta has been announced, here‘s the What’s New page with the download link. The most important thing is right at the bottom:
API for adding custom file indexers
New COM API allowing third-party developers to create plug-ins enabling new file type indexing (view PDF documentation)
That’s a feature that’ll really set them apart from other products, plus it proves to me they are really listening to their customers: I’m one of those who requested that feature in the past. I’ll be sure to have a very close look at that thing.