Loading Smart Energy (SE) firmware on one of our ZigBee (ZB) modules will give you the uncertified RF stack needed to work with Smart Energy applications. I say "uncertified", because in order to be a certified ZigBee Smart Energy product, certain testing must be done to ensure SEP compliance.
The Smart Energy application itself however is at the application level, which is higher up than the protocol-focused RF stack. In the case our our Smart Energy Gateways, we've created our own proprietary python application called the Smart Energy Framework, which serves as the "glue" between the hardware at the Smart Energy network level and the Device Cloud where that data is pushed, then available for consumption by customer applications etc.
In order to replicate what our ConnectPort X2e for Smart Energy is doing, you'd also need to create an application from which could take the various data within the ZCL, and format it in such a way that your application can display or use it.
Another possibility might be that you buy one of our Gateways (perhaps one as part of the Smart Energy Developer's Kit?), then use the Smart Energy Framework already on the Gateway to accomplish whatever task you wanted to develop an app around. Your app could then focus on polling the Device Cloud database with RESTful queries, to display whatever data you wanted (or setup a PUSH monitor to have it pushed to you).