GNU TeXmacs
Summary
GNU TeXmacs is a free scientific editing platform with a WYSIWYG interface for building structured documents containing text, mathematics, graphics, and interactive content. It can function as a front-end for computer algebra systems, supports multiple formats (TeXmacs, XML, Scheme) and offers converters to TeX/LaTeX and HTML/MathML, all while emphasizing high-quality typesetting and extensibility via Scheme.