XML Copy Editor is an open source XML editor with DTD/XML Schema/RELAX NG validation, XSLT, XPath, pretty-printing, syntax highlighting, folding, tag completion/locking, a spelling/style check and, on Windows, lossless import/export of Microsoft Word documents (quoted from the project site). Of special note is its support for TEI DTDs and Schemas.
XML Copy Editor is released under the GNU General Public License (GPL). It is written in C++. Version are available for Windows and Linux, with many distribution-specific packages available.
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