I've followed the instructions at https://github.com/publiclab/plots2, but I'm running into problems because of not being able to use Gnu make natively on Windows. There are solutions, but I chose to explore other options before trying those.
One solution: switching to Linux.
The Ubuntu LiveUSB doesn't have a driver for my WiFi card. However, I know that I can get it working because I've done it before. Con: it's going to take me a day or two to set up.
Solution to that: working on somebody else's working Linux/Mac machine.
We found OpenLayers yesterday: http://openlayers.org/en/latest/examples/ What I understand of its core functionality is that it allows one to have custom tiles for a map (https://en.wikipedia.org/wiki/Tiled_web_map), so you can change the the primary data shown by the map and also its look and feel. There is more to the library though, as you can see from the examples. I have to explore this and the current website some more before being able to say if it is right for our project (unless you want a complete redesign).
What map service does metamap currently run on?
Some more promising links:
http://wiki.openstreetmap.org/wiki/Overlay_API http://wiki.openstreetmap.org/wiki/Khtml.maplib http://wiki.openstreetmap.org/wiki/FacilMap