To back up a bit - does everything we want to use in Poser that is exclusively for Genesis require this “Companion” file? What purpose does that file serve? Are we out of luck until there is some kind of universal compatibility “importer”?
Yes you do need the companion files (note the -s - more than one file per item).
First, you need a file that Poser’s library can see, so you can see and click on it. Poser’s library only sees Poser format files, like cr2s, pz2s, it doesn’t see DS format files like .duf and .dsa.
And then you need a python script that tells Poser and the DSON plugin to load the DS figure or preset or whatever, and where its files are.
So you see the cr2 in the Poser figure library (because Poser will show you any file in there with a .cr2 filetype, whatever is actually in it, and try to run it if you click on it), and it isn’t a ‘real’ cr2 in terms of having all the data for a figure a Poser cr2 usually has. But what it has in it (and all it has in it) is a command to Poser to run the associated python script.
So, you click the fake cr2, the fake cr2 makes Poser run the python script, and the python script gets Poser and the DSON Importer plugin to load Genesis and the morphs and UVs and whatever from the DS format files in the data folder.
So - you can only use DS content that is (i) in the DSON format (which is very new, so older DS content can’t work until it’s been updated), and (ii) has the companion files - the python script to get Poser to load the DS content, and the fake cr2 that starts the matching python script.
If you do nothing yourself, you will have to keep checking which products are DSONed AND have the companion files. If you get DS4.5 installed - not to build scenes and pose and render in, but just as a tool - then you can create the companion files yourself. There’s a simple menu entry to click on to make the Poser comanion files at a simple click. And with not much more complexity you can even load old, non-DSONed DS products, resave them in DSON format, adn then click for the Poser companion files. Then you wouldn’‘t have to wait for DAZ or PAs to update their products to DSON and/or produce the companion files.