Take a look at this: http://visual6502.org/

Also for some background watch: http://www.youtube.com/watch?v=uP1gWg5ezyY

The idea would be implementing the simulator that could be useful as a replacement for JScript Sim, as a library for emulators using the chip, or both. In some part of the video is demoed a C implementation of the simulator running a COMMODORE BASIC start up process which would somewhat fit in the "simulator library" category.

If this is a bad idea yet I hope you enjoyed the information provided in the links above as I did

This project is interesting but really useless.
And how these people can use Java script for such project????

good idea, bad idea? It's a cool idea. Looks like the people involved are having fun in digging through things to discover the logic behind them.

Welcome back LocoDelAssembly after almost five months. I hope you had a good holiday camping in the mountains of inner Mongolia.

As for the simulator: Do you intend to write an assembly version to try and gain more speed? Or is there another purpose?

Yes, for this purpose. Since they mention they will be providing a GPU version, then I assumed that perhaps well-written ASM and also making use of SSE/AVX and maybe some threading may help here to speed up over the (not public yet) C version.

JohnFound, the purpose of doing this (besides historical preservation purposes), is to make more accurate emulators.

Seems like overkill for an ancient cpu. All you need for good emulation is accurate cycle counts for each instruction and each addressing mode.

some stuff for this: http://www.waitingforfriday.com/index.php/4-Bit_Computer