Do we need to install this on top of ECC 6 or is it integral part of it.
If we need to install on top it, does that we need to purchase it ?
It's not part of SAP ECC 6.0 licences. You need to additionally purchase it.
It's SAP NetWeaver Portal based solution and sits on top of SAP central components including SAP EHS.
So, you not only have to buy separate license, but have to ensure so many other technical prerequisites for implementation.
Please visit the following link for detailed info.