Well, never say never, as some day, someone will prove you wrong...!
But, I think the circuits that they are talking about are taking the display hardware to a higher level, compared to the dk'tronics and similar systems.
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Yes it's possible, either Wilf's way, which I might add is pretty ingenious but can be broken with custom display drivers
OR
You can emulate the ula externally and re-create the alternate address lines perfectly, definitely more complex this way but it will behave exactly like the internal UDG
Regards Andy
what's that Smell.... smells like fresh flux and solder fumes...
"The Earth is just too small and fragile a basket for the human race to keep all its eggs in." ― Robert Anson Heinlein
Elektronika MK61, Psion series 5mx have now. Many years ago had Spectrum 48, 128k/TRDOS and Amiga A600 ...
If I understand this circuit right, it is not UDG, as all characters are in an EPROM. There is no RAM, so no characters can be user defined. (Except you have to reburn the EPROM.)
Standby alert 
