(Samples taken from the Droidscript documentation)

The SetOrientation method forces the screen to either “Portrait” or “Landscape” orientation. After using this function rotating the phone/tablet will have no effect on the app's orientation.
To unlock the orientation call the function again using the orientation “Default”. The optional callback function is invoked after orientation change.

app.SetOrientation( orient, callback );

function OnStart()
{
  app.SetOrientation( "Landscape", OnOrientationChanged );
 
  lay = app.CreateLayout( "Linear", "Vertical" );
  txt = app.CreateText( "Hello" );
  txt.SetTextSize( 32 );
  lay.AddChild( txt );
  app.AddLayout( lay );
}
 
function OnOrientationChanged()
{
  app.ShowPopup( "Current orientation = " + app.GetOrientation() );
}

The GetOrientation method gets the current orientation of the phone/tablet. It will return either the value “Portrait” or the value “Landscape”.

orient = app.GetOrientation();

function OnStart()
{
  orient = app.GetOrientation();
  app.ShowPopup( orient );
}

The GetDefaultOrientation method gets the default (normal) orientation of the device. It will return either the value “Portrait” or the value “Landscape”.

orient = app.GetDefaultOrientation();

function OnStart()
{
  orient = app.GetDefaultOrientation();
  app.ShowPopup( orient );
}