Is anyone aware of a free and open-source solution for creating OpenType VFs? And yes, I'm well aware of the commercial solutions; I'm not interested in them. Right now, I am aware that FF has some MM support (not OT1.8) and METAFONT can create variable fonts, of course, but again, not of the OpenType variety.
[Addendum: I guess it is possible in some way to do, by creating a file manually, and the using fontmake, but this is extremely painful and not practical. But maybe that is the way to go.]