OmniHelp is a cross-platform, browser-independent, tri-pane help viewer built in pure JavaScript and CSS with HTML 4. Some functions (such as help embedding) may in the future be in Java, C, or C++; CSH is fully supported. All code is under the LGPL.
An alternative to the page-chapter-paragraph documentation approach. LivCos allows you to teach the computer the structure of your content, so it can support you in various contexts. Pages will be generated as one of many views on the actual content.