I published a basic DesignSpaceEditor extension for RoboFont. Available from RoboFontMechanic. It is a single window with panels for axes, masters and instances. It follows the DesignSpace document format. No preview and a maximum of 5 axes.
New Superpolator can import and export DesignSpace files. The formats are similar, but there are some differences and not all data can go everywhere. Read up at the Formats page to find out what is exported and what is not.
A video of the Superpolator3 Preview during the 2012 Robothon. Oh boy, a lot of work that still needed to be done. This is a presentation from the 2009 Robothon on Superpolator2 and Prepolator, together with TypeSupply’s Tal Leming.