Can application templates be shared among applications?

Can application templates be shared among applications?
Some people think that the spec allows this but it does not seem clear to me.
So, at a minimum we need to clarify.

If application templates can be shared then we need to clarify lifecycle.
Under what circumstances do application templates continue to live after the
application that created them terminates.

Also, how do we specify which application templates can be shared and which
templates cannot. I may be running a top-secret application that I want no one
to be able to access. Or, I may be part of a group that would like to share
components.