Debian/kFreeBSD vs linux jail?

[Joshua Isom]

Considering Debian's ported the "standard Linux userland" to the FreeBSD 
kernel, I'm wondering if it's possible/practical to use Debian inside of 
a jail instead of a Linux CentOS jail, which has been documented.  I 
know some applications are linux specific, but are they really linux 
specific or gnu specific?  I'm going to retry getting a printer driver 
working with cups that had issues with FreeBSD in the past, but I don't 
know if it's FreeBSD userland or FreeBSD kernel that caused the quirks. 
  Has anyone tried using Debian's kFreeBSD userland inside a jail?  Is 
it just pointless on a FreeBSD system?