An updated version of the AFDKO with early experimental support for building OpenType/CFF2 variable fonts is now available at the Adobe AFDKO website. Please take a look at:
http://www.adobe.com/devnet/opentype/afdko/AFDKO-Variable-Font-Support.html.
What is different is just the command 'buildMasterOTFs': it now expects a different directory tree of source material. This version of the AFDKO will work with the 'AdobeVariableFont.otf" OpenSource files at https://github.com/adobe-fonts/adobe-variable-font-prototype.
- Read Roberts