There's some information
HERE about the release of the ROM files.
"In mid-2000 Hewlett-Packard released the 48SX/GX ROMS to the public. Previously protected by copyright, the only true way to get a ROM image was to dump the ROM of your own calculator..."
I would assume most people who use the 48GX emulator are people who once owned the calculator and got used to the keystrokes and getting results reasonably quickly. Perhaps (like me) writing programs specific to their job. I've owned 2 of them, only one survives (they didn't have screen protectors back then!). I used it so hard that I almost know where the keys are instinctively. That is, as long as the keys appear as they used to. Hence, my interest in a "real" emulator skin.
The calculator is a decade old and is no longer for sale. There's better stuff out there, with color screens and more intuitive input.
If you are looking for a new calculator, and never used the 48GX, I wouldn't be surprised if you give up on it quickly. Pocket Excel or relatively inexpensive calculators can achieve the same thing without the learning curve.
That said, there's a bunch of educational value in this calculator, and you may find it interesting what "cutting edge" was some years ago. Mine had a 256K memory card that was not flash, it requires a 3V lithium battery to keep the memory. I also purchased a calculus rom card, which extended more functionality and 3D graphing capabilities. This was my "Pocket PC" when I was in college.
Seeing how far we've come in a decade makes me wonder if we will be as nostalgic about our Axims in just a few short years...