Note: US law, obviously (these points are moot in EU due to strong laws for interoperability).
Contracts can legally bind the developer/s with this, more so if it is a corporate entity. Even if Google wins this case and the APIs cannot legally acquire copyright protection, the third-party can sue the developer/s for disclosing trade secrets. The code legally is clean (IP-wise) at this point, but the developer/s have broken a contract with the third-party provider in doing so, and they can sue those developer/s (however, any users of the released code are protected since they are not the signatories/parties to the contract).
Contracts can legally bind the developer/s with this, more so if it is a corporate entity. Even if Google wins this case and the APIs cannot legally acquire copyright protection, the third-party can sue the developer/s for disclosing trade secrets. The code legally is clean (IP-wise) at this point, but the developer/s have broken a contract with the third-party provider in doing so, and they can sue those developer/s (however, any users of the released code are protected since they are not the signatories/parties to the contract).