Note: this is probably not the repo you're looking for. This repository contains the code for the legacy version of MindMup, which was discontinued on January 1st 2017.
For the visualisation library used to create interactive maps in MindMup 2, see the mindmup/mapjs github repository. This is the part of MindMup that paints mind maps in HTML/SVG and allows you to build interactive mind maps applications, compatible with the MindMup format.
The MindMup 2 web site is not opensource, and we currently do not have plans to opensource it fully.