We distribute an application with a small, embedded servlet container. We
let people create their own JSP pages in that container, and they have to
write java snippets to get at our API in their pages. This is fine, except
that 1) it requires them to know Java, and 2) it requires that they have a
JDK on the system, instead of just a JRE, to compile the pages. Or else it
requires that they put a copy of tools.jar on the path, which brings its own
problems.

I'd dearly love to get away from forcing my customers to write java code to
do anything useful.

What would be great is to switch to some system where they could add
html-like tags into the pages, and the container would be smart enough to
parse the tags and replace them with dynamic data.

We looked at Struts and tag libraries a few years ago, but it was way too
complicated. We looked at FreeMarker, which is closer to what we want, but
found it a bit limited (at least it was a couple years ago).

What are the best choices out there for doing this kind of thing?

Some of our competitors have their app return XML, which is then transformed
to web pages by XSLT. This is just plain dog slow, though.