Thank you! This addresses a real need in the open source hardware community.
Is USB-IF aware of this[1]? Would they see this as a violation of the spirit of the current terms in the sense of the revenue loss, and come after pid.codes for every $500 application they feel you might owe them? I'm optimistically hoping that you've discussed this with USB-IF and that although they may not officially endorse or support, they won't actively try to stop what you're doing.
[1] >>This site is in no way supported or endorsed by USB-IF.
EDIT: I should have read the FAQ[2] where you address this question specifically under "Won’t you get in trouble?"