Hi Bhakti,
Please do not use River RDE. It is the name for the early predecessor of WebIDE, but has not been supported for at least two years. Whatever application you use for Goods Receipt, you will need to do some customization to implement the RF Gun. What I recommend is doing some research using the Google Custom Search which hopefully will point you in the right direction. I would also look for content on Hybrid Application Toolkit which is where many folks implement such capabilities in particular devices. While I know there are a lot of image capture/scanner interfaces that have been documented, I am less certain about RF Guns. However, I suspect that most of the interface extensions are going to be the same as other data capture devices.
Good luck!
Regards, Mike (Moderator)
SAP Technology RIG