That's why I said emulator. I should have searched before posting, but apparently there is already at least one product on the market that does this (Helicon Ape).
I think what I did, when I was using lighttpd with Wordpress, was to look at the .htaccess files that were being used, then translate them (by hand) to lighttpd rules. It requires a bit of expertise in both Apache and in whatever web server you're using, but it's another solution to consider if you're looking to "use" .htaccess files.