This problem is seen in Celestia v1.5.1 and v1.6 built from svn.
Global variables (i.e. variables not prefixed by "local")
collide among the ScriptedOrbits and ScriptedRotations
of different Modules in different Addons.
They should not, since equivalent global functions do not collide.
This Addon demonstrates the problem.
The non-local variable global.var is declared at the top level of Addon_1's Module_1 and set to the value 1.
The non-local variable global.var is declared at the top level of Addon_2's Module_2 and set to the value 2.
Addon_1's Module_1's global.var is overwritten by
Addon_2's Module_2's statement
global.var = 2
It should not be overwritten.
I've attached a zip file of the Addons which demonstrate this issue.
A concern is that some unpublished Addons may be using this inappropriate functionality for inter-Addon communication. I must admit that I'm strongly tempted to do so myself.
I could not-so-reluctantly be persuaded that this functionality should be retained and documented.