EDITED POST SOLUTION FOUND: This worked on the white PDN, with the default firmware and not using ADB at all. Perhaps this will work on the black one.
1- Put your launcher apk of choice on an SD Card (ie. the root of the card, so easy to get to). For this test, I'll assume it's called "launcher.apk", on the root of the SD card.
2- Open the PDN web browser and type:file:///sdcard/launcher.apkThe
"unknown sources" message will pop up, and will direct you to the settings area to enable Unknown Sources (which you want to enable). At this point, you have to reboot because there's no back button.
3- After the reboot, go back into the browser and type the same command. This time, you can install the apk, and again reboot when done. After the reboot, you'll get the "Complete Action Using" launcher screen, choose the new launcher and you are in. From there, you could install other apk's the same way, or maybe add a terminal app, file browser, and of course USB Debugging.