Quoting Markus Kilbinger,

[...]
> - How to configure a working Linux compatible NetBSD system? Any
>   further libs, binaries?

Have a peek at the compat_linux(8) manual page. You will need to
set up an environment in /emul/linux, which mainly means you need
to copy some Linux shared libraries and the dynamic loader there.

> - What about X11-Linux binary compatability under Linux?

This should just work, as there is, from an emulation point of view,
nothing special about X11 binaries. You will need the Linux versions
of the XFree86 shared libraries and install them under /emul/linux.

If you have done all this, give some more information about how
things are failing (do you just get Exec format error messages, or
does it start up but fails on a missing system call, or..)

- Frank