Using on screen keyboard and barcode scanner with iPad.
It depends on the bar code manufacturer and which Bluetooth profile they use.

Most will use the HID (Human Interface Device) which will make it emulate a keyboard.  Some will have a button that triggers the on-screen keyboard to come up while others will use a different bluetooth profile (like SPP - serial port profile) that will allow data to come in via a different avenue.

The Socket Mobile Bluetooth scanner supports the extended Bluetooth profiles like SPP and MFi-SPP (Application Mode).  From their datasheet:


  Application Mode - Improves business productivity with faster,
  efficient and reliable data transfer over Bluetooth; leverages
  Application Mode functionality by integrating Socket Mobile’s SDK in
  app


Basically, that a fancy way of saying the BT scanner communicates directly with the App and not as an HID device meaning the on screen keyboard (or another BT keyboard) is free to be used.