Yes,. the Poser CF (Companion File) is ONLY for poser 9 or better,.
As far as I know,. it won’t work without the DSON importer, which is for P9 and PP2012 ..and none of the genesis stuff will work in earlier versions of Poser.
If you have DS4.5 installed, (needed to use genesis in Carrara 8.5) then I’d download the Daz versions. as the C8.5 beta will read Duf format.
If you have Poser 9, or Poser Pro2012, and the DSON importer (needed to use genesis in Poser 9) then you can download the Poser versions.
If you have Older versions of Poser,.or Daz Studio then you can’t use genesis products, and if the “product” isn’t for genesis, then there shouldn’t be any issues, ..
V4 can be downloaded and installed to either DS. (Content / My Library) , Poser (Runtime), or a customised runtime folder.
It’s a bit confusing right now for everyone, especially for new customers, with multiple format downloads for any single product,. but there are plans to make things easier.