CaH4e3 updated his site with the following message:
- Dance 2000 12-in-1 (Unl)[U][!]. One more old dump now emulated. As usual it took too long, and as usual it was too easy to guess. Game is similar to many-many Dance Dance Revolution clones from our chinese friends, but in addition to all other similar carts, this one allows you to use two 4k CHR tables for the background rendering on the single screen without using mid scanline pages switching or IRQs. It's operates just like Oeka Kids cart, but with just 2 pages for two nametables instead of 4 for 4 accordingly.
As usual, you can play it only on latest FCEUmm version or on the SVN version of FCEUX.
News source: http://cah4e3.shedevr.org.ru