Linux is famous for being ‚open source‘ in that the source code for Linux plus all the applications is normally available for those who want to view or modify it.
However, not all Linux programs are Open Source. Some are ‚closed source‘ in that the developers who create it would like to keep how they created it a ’secret‘. The argument here is that the company or developers have invested time and money in creating a program, charge for their work so why should they go releasing the code to any Tom Dick and Harry.
Personally I have no issues with this, there are some good programs for Linux which are closed source. One such program is the flight simulator X-Plane. X-Plane is a paid for program and the 6 dvd set contains versions for Linux, Mac and Windows. It is in my opinion the best flight sim available for the PC.
X-Plane contains subsonic and supersonic flight dynamics, allowing users to predict the flight characteristics of the slowest aircraft to the fastest. X-Plane includes thirty-five aircraft on its master disk, spanning the aviation industry (and its history), sporting aircraft from the Bell 206 JetRanger and Cessna 172 to the supersonic SR-71 and the Space Shuttle. Additionally, more than 1,400 additional aircraft models (such as those at X-Plane.org) can be downloaded from the Internet , nearly all of which are free. If those aren’t enough, users can design their own airplanes and test fly them!.
To Install X-Plane on Ubuntu 9.10, hereis a great article working through installation X-plane on Ubuntu linux 9.10. For other distributions see this page.