This post was written 2010-04-29.
I'm using blogger to chronologically sort this stuff out and provide a back story.
According to my profile on the Org I signed up on the 6th of March 2004.
I'd been lurking for a couple of weeks at least and I signed up to announce my XNO utility.
XNO was a small, stand-alone Windows app that talked to X-Plane using UDP 7.15.
The UDP format was quickly broken, I started learning how to put plugins together.
Sometime later XNO2 was born as a native plugin for Mac and Windows. I can't remember if I did linux.
This plugin contained my very first incarnation of the DRM system, it used a license key system that contained the users email address as a deterrent, the idea being that everyone hates spam, and I'd know who was sharing.
The plugin sold moderately, most people would purchase first and try and figure it out later, not really the idea behind demo-ware. You could try it before you bought it, for about 10 minutes.
The result was that a lot of Mac users were eagerly sending me money and then finding out that they had purchased a Windows only product. A lot of refunds were issued.
Eventually I released XNO2 as freeware with a donation requestion, very few people ever donated. Occasionally people send me a dollar. Come on, seriously, a buck?
Oh, the purpose of the plugin? To talk to the GNS-530 package.
You can still find all this stuff out there, people keep it alive, just Google for XNO2/GNS-530/X-Plane and you should find it.
Personally, I recommend just grabbing the Reality-XP add-on.