Ah yeah, according to
QWSKeyboardHandler *QWSServer::newKeyboardHandler( const QString &spec )
{
  QWSKeyboardHandler *handler = 0;
  QString device;
  QString type;
  int colon=spec.find(':');
  if ( colon>=0 ) {
    type = spec.left(colon);
    device = spec.mid(colon+1);
  } else {
    type = spec;
  }
  if ( type == "Buttons" ) {
#if defined(QT_QWS_SIMPAD)
    qDebug( "QWSKeyboardHandler: using SIMpad switches handler..." );
    handler = new QWSsimpadButtonsHandler();
#elif defined(QT_QWS_YOPY)
    handler = new QWSyopyButtonsHandler();
#elif defined(QT_QWS_CASSIOPEIA)
    handler = new QWSVr41xxButtonsHandler();
#endif
  } else if ( type == "QVFbKeyboard" ) {
    handler = new QWSVFbKeyboardHandler();
  } else if ( type == "USB" ) {
    handler = new QWSUsbKeyboardHandler(device);
  } else if ( type == "TTY" ) {
    handler = new QWSTtyKeyboardHandler(device);
  }
  else if( type == "Samsung" )  {
    handler = new QWSSamsungKeypadHandler(device);
  }
  else {
    qWarning( "Keyboard type %s:%s unsupported", spec.latin1(), device.latin1() );
  }
you may have more luck with QWS_KEYBOARD="Buttons"...