Is this just an nroff and dBCodes thang, or can it be used in HTML?
It's a typesetting system oriented toward the use of mathematics. It existed before dBcodes or HTML ever existed.
There is a "latex2html" command for linux. Also wordpress has a latex plugin for its blog software. And I think Google's "blogspot" has something similar.
What typically happens with "latex2html", with the wordpress plugin and with dBcodes support, is that those use just the mathematics rendering part of latex. They use latex to typeset a mathematical formula, then make an image of that. Then the display the image in the web page. Percy would know more about that part, since he implemented it for his forum software.
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However, I found that on the CodeCogs site. I don't know them and here I am pulling one of their scripts into my site without knowing what all it does. I also don't know which browsers they support or whether their support would continue.
So some way to generate an image of the formula would probably be best unless there is some generally available way to support latex in HTML.