I suspect the answer is to sign up for a multi-million-dollar license from TeleNav or somebody.
The reason the API was pulled was because Google itself has limitations on what it can do with driving directions (e.g., cannot do real-time turn-by-turn stuff), since Google licenses this data from TeleNav or other firms. Google, in turn, cannot let developers do those restricted things, and an open API cannot be adequately protected for this case.
I thought I saw mention that Open Street Map has driving directions, FWIW.