To me, equating "code" with "open source" is so early 90s. The closest analogy I can think of is equating "doctors" with "health care". While doctors tend to get the glory, there is a whole ecosystem of paramedics, RNs, candy stripers and volunteers, technicians, midwives, administrative staff, etc. and etc. that keep the health care system up and running. As open source projects mature, they go light years beyond a developer scratching an itch into ecosystems containing foundations with administrative staff, advocates, lawyers, conference organizers, trainers, support contracters, technical writers, and so on.
So, at the risk of raising the ire of women programmers everywhere, I propose that the problem to be solved isn't "how do we get women to program in open source?" but rather "what are the roles in open source and who can we get to fill them?". I think that projects who can define and enable their roles will be both richer for the experience and pleasantly surprised to see how many women pop out of the woodwork.