Nonfree software is a major part of nonguix, both because of the ethical problems which are the raisons d'être of the GNU project, there's also the more practical consequence drom the nonfree nature, that you can't bootstrap the binaries any you can't know their provinence beyond "it's from the vendor".
However just to clarify for others, it's not the only thing there of course. There is free software in nonguix, maybe because it's PITA to bootstrap, like for example Leinigen and other parts of the Clojure ecosystem, as well as everything and anything written using Electron. And of course notable free software things there are also the blobbed Linux kernel (probably obvious reasons), as well as Firefox, since Mozilla has some interesting trademark opinions, so you can't have it on the main Guix channel.
However just to clarify for others, it's not the only thing there of course. There is free software in nonguix, maybe because it's PITA to bootstrap, like for example Leinigen and other parts of the Clojure ecosystem, as well as everything and anything written using Electron. And of course notable free software things there are also the blobbed Linux kernel (probably obvious reasons), as well as Firefox, since Mozilla has some interesting trademark opinions, so you can't have it on the main Guix channel.