Actually I appreciate the license questions, because it makes it easier to know how to re-write the docs to clarify.

One license allows you to develop one product. If you stop work on one thing you can re-use the license on something else, though --- it would be silly to ask at what point a change of focus becomes a different product.

This seemed the sanest way to do it. I think per-site, per-user etc licenses are really stupid. The license then impinges on your technical decisions.