I've used a http://www.vmware.com/ virtual machine with vmware 3.2 for software development with a Netware 5.1 and a Netware 6 evaluation copy. Netware 5.1 includes a 16-color VGA X server, but Netware 6 does not, and vmware 3.2 cannot display more than VGA without their special vmware X server being installed. You need the X Server for first-time configuration, later you may do everything required from a Windows VM. NW5.1 SP6 does not seem to include the 16-Color VGA X server any more. I also failed to update the 5.1 config to NW 6 and NW 6 refuses to run on my older K6/2-300 box. Markus has tried to install NW 6 on the VMWare 4 beta but it failed. With the help of Günter Knauf mailto:info@gknw.de I found that an already installed VMWare machine installed using VMWare 3.2 on Windows 2000 can be used with vmware for linux as a testing environment.
I've ported the wxBase portion of http://www.wxwindows.org to Netware and based on this I've ported a big application for a client with success, but not yet mass-distributed.
For debugging I've used a serial cross-over cable to connect COM1 and COM2 of my Linux box together and connecting gdb to /dev/ttyS1 and vmware to /dev/ttyS0.