WIC offices vary widely, depending on the state and the umbrella organization through which they're run. Sure, many of the nutritionists are bureaucratic and their "nutritional" advice is far from anything that I believe, but many others are extremely dedicated and well-informed, and make the sacrifice of working within the system in order to have the access to people who might otherwise not be exposed to more holistic viewpoints. (I know one WIC nutritionist who leads classes in babywearing, cloth diapering, yogurt making... and they are attended by moms who might not otherwise be exposed to this stuff) In my experience, as a mom receiving the benefits (mostly for the free breast pump) and then, for a time, working there, the priority of the people who work for WIC is to keep their numbers up and maximize their access to "at risk" families. They don't care how many of the checks you actually use or what you do with them, and while they can't officially condone your donating the stuff you won't use, when you think about it, the stuff they offer is mostly the stuff that our government heavily subsidizes, leading to surplus, anyway (conventional dairy and cheap grains- industries which are entirely propped up by subsidies). Why not let it go to families who might use it? I wouldn't ever use the formula- and I can't speak for whether you'll be able to offer breastmilk to your foster child- but whatever part of the package you're not going to use, why not just drop it at the food bank? (For a mom in great need, even if she's already on WIC, it's not going to cover all her food costs, and that stuff could make a big difference; also, WIC is only available to families who are here "legally", so for immigrants without legal status, those donations could also make a huge difference). Again, none of this is legitimate- I certainly wouldn't tell anyone "official" that I did this- but I do it myself, and if it's stealing, then it's "robin hood" style stealing and I'm okay with that. The government is already paying for big agriculture to grow these surpluses, WIC can only maintain it's funding by keeping it's numbers up, and I'm certainly okay with passing those surpluses on to the truly needy. What I've done is used the things that we'll use- the vegetable voucher, the cheese (you can actually get Cabot, which is RBGH free), the rice, and gratefully accepted their breastpump, and pass on the rest of it to people who need and more than we do and will use it.
A quick rundown of how the WIC program works now, because it's changed a little bit over the past year (I have no idea if the children's packages differ for foster families as part of the stipend)- they offer checks for food (the aforementioned conventional dairy stuff, cheap grains "cheapest available" eggs) as well as a few other things, the most valuable of which is a token $10 fruit-and-vegetable voucher) to the mom through pregnancy and the first six months of the baby's life- if the mom chooses to breastfeed, she receives a much larger food package, rather than formula, as well as unlimited free breastfeeding support. If the baby is formula fed, the mom still receives food for those six months, but less of it. The baby gets formula, and starts getting his own food checks starting at six months, when the mom is no longer eligible (even if she's nursing...), the baby continues to receive food until age five (but less- and far less than the pregnant moms).