Map saving

Very good point. The problem with something like googlemaps is that THEY control your mapping capabilities. If they change their policies or have a bad hair day, your ability to offer maps is gone. I like this module because it goes in the opposite direction. Personally, I would rather have everything installed locally, which is basically what your request advocates. Using ANY third party/client software outside of drupal for a service is taking a risk. I second this request.

I assume you mean the demo from http://nightly.communitymapbuilder.org/mapbuilder/demo/contextEditor/ind....

Doh! Yep, that's exactly what I mean and did not see. If I understand everything correctly, I can create my own maps, add as many layers as I wish and reuse them in my application, correct?

According to the help text at the demo page, you can add existing map services to your map, and then save that as a context file containing which maps are displayed (or hidden) and their bounding box.
Last quote from the demo page:

Finally, when the map is ready to be saved, click on the"save" icon on the left side of the map. This will save the map as a Web Map Context document which can be used in other applications.

If this mapbuilder module would present a button to save map contexts, it would also need to offer the possibility to display given map contexts.

A 'Save' button will be added to the mapbuilder module. The MapContext page will get an option to read the layers from a context file.

Fixed for mapbuilder library version 1.0.1.