I was also wondering what that linux claim means, so I just sent them an email to ask. Hope they get back to me with an actual answer.

It's mostly normal Android from what I can tell. There's also Kobo where all of their devices are Linux based, although it's more of an embedded Linux system with limited flexibility, but you can install koreader on them along with some other mods.

And there's the Onyx Boox series which run Android as well, although they seem to have retired most of their B/W devices.

I love my A6X2 Nomad, it's a great device. Note that it's an Android based device. For me, I have no interest in hacking it, side loading Android apps, or running Linux on it. It does exactly what I want it to out of the box and serves its purpose perfectly as a low power digital notebook.

I have the nomad, and I love it. I use it every day for taking meeting notes and it hasn’t let me down yet.

Their current OS is android based (I think) and works fine, but I am excited about a Linux version replacing it.