I don't know, but in this case, I don't want to embed fonts, I don't know how LuaTeX can do that
LuaTeX knows how to not embed fonts if you ask it not to, but I'm not sure how this is handled on the ConTeXt level.
but it runs really slow on my ancient PC, especially on the first time when it's generating font cache.
That's true, it needs a lot of memory (so most of the time is spent swapping, I guess). As I've found out, Mark IV is slightly faster on a 450 MHz Sparc processor with 1GB memory than on a 2GHz Intel Dual Core with 512MB memory ;-) But is it still too slow after the first pass?
I convert it to ttf only because I want the tfm files, I can't find there's a tool that can to otf2tfm.
Actually there is one that comes with the lcdf typetools. It even ships with TeX Live. Arthur