I have a suspicion that's probably the system that's dumped as "Hot Dance 2000". Given that it says "Dance 2000" on the mat itself and "hot dance" on the package, it only seems logical.
("Hot dance"...
literally. Lulz.)
Edit: Then again, perhaps not; the thing claims to have stereo sound, which a Famiclone obviously doesn't. But then again, the packages for these things are usually covered in blatant lies, so yeah...
Edit #2: The manufacturer appears to be "Soyin", as one can see if one squints at the upper-right corner of the mat.
This appears to be them, judging from the logo; they're now known as
GreatHouse Electronics and don't sell any dance mats even on their Chinese site. Granted, it has been over 10 years...
Edit #3: And the Internet Archive proves useful again! SY-2000-04 is the first product listed there. The things were sold in bulk, in packages of... you guessed it... sixteen. Alas, no demo video or anything, not even a spec list or song list or anything.
More bootleg-DDR history, courtesy of maxzhou88:
original Chinese post and
Google translation. Seems that there are even
more variations of Hot Dance, GLK Dance and Dance Xtreme out there, all of which appear to have originated in the Baoan district of Shenzhen. There's even one version that has the Hot Dance graphics but the Dance Xtreme/Dance Master UI.
Alas, I couldn't find the dump of these four versions on his file storage (anyone who knows sufficient Chinese want to comment to tell him the file's missing?).
Edit: Ooh! One of them is Mix Party 2001! Apparently it's a Famiclone with an added chip for digitized sound. Can't tell if it's the VT03 or not; the photo is rather blurry.
He also claims there's a dance mat that uses Megadrive-compatible hardware, but that he broke it trying to rip it. -_-;; So maybe that one Gold Leopard King box really is telling the truth.