Belgium has released an official software for their eID card. That software is a modified version of OpenSC. The information and software can be found on eID-Software website.
OpenSC > 0.10.* includes support for the Belgian eID card, except for legally binding signatures (with the so-called Signature key) as this requires a GUI, which is not yet available/implemented.
For more info:
Thanks to Belgium for choosing OpenSC as basis for their software and donating the full source code back to use under LGPL license. Thanks to Zetes for their support of OpenSC.