Other LWJGL demos at other sides work for me, but not the ones at www.lwjgl.org/demos.php The error I get is the following. It sounds like the file has moved:
An error occurred while launching/running the application.
Title: LWJGL Demo [test.SysTest]
Vendor: LWJGL
Category: Download Error
Unable to load resource: http://lwjgl.org/jnlp/lwjgl-linux.jar
They still work just fine.
Using 1.5 huh? Well, 1.5 is kinda broken… it’s a “beta” as in “b0rked” 
Oh and if you are reporting errors don’t omit all the details (Machine, OS, Java version etc).
well, the problem is that I haven’t added the linux jar (oops). I’ll update the demo page when 0.92 is released (RSN)
Not using Beta. System spec beyond “Linux” shouldn’t matter here. No “Linux” will work if the linux .jar isn’t there.