Nokia have released the Nokia 6131 NFC SDK available from the above link or here. Installation guide is here (pdf)
The Nokia 6131 NFC SDK allows developers to create and emulate Java applications (MIDlets) for the Nokia 6131 NFC mobile phone. The SDK includes the Contactless Communication API (JSR-257) which enables the use of the Near Field Communications (NFC) features of the Nokia 6131 NFC. In addition to the standard JSR-257 APIs, the SDK includes Nokia NFC specific interfaces and classes. The Nokia 6131 NFC SDK contains a Nokia 6131 NFC phone emulator, Java APIs, sample MIDlets, and documentation."