1. Start IDE on fresh user dir. Open .../contrib/explorefromhere as a module
project. Select Reload in Development IDE from context menu. It is installed as
expected. Open Module Manager and locate this test module (will have expected
red T icon). "Uninstall" button enabled; if pressed and dialog confirmed, the
test module is disabled and deleted as expected. (BTW why is the Delete key not
bound to Uninstall? Would be convenient.)

2. Now make a new standalone module project (not in nb.org). Again reload in
current IDE and again locate in Module Manager. It is displayed but the
Uninstall button is disabled when it is selected. You can disable it, but not
delete it. (By which I mean removing it from the module list, not actually
deleting the JAR file.) Furthermore, if you invoke Properties on the context
menu, rather than the usual module properties you get properties suited to a
module display category!

3. Now open the standalone module project's properties dialog, and in Display
change Category to e.g. Database. Close (OK) and Reload again. Now in its new
location in Module Manager it shows the correct module properties, but Uninstall
is still disabled for it, even after restarting the IDE.

There is no apparent way to make this test module disappear from the Module
Manager, besides manually deleting the $userdir/config/Modules/*.xml entry. I am
not sure how it differs from the explorefromhere case, but somehow it does.

In NB 4.1 you could just select such a module and press Delete and the entry
would be removed (JAR untouched).