| Need | Open source | Commercial |
|---|---|---|
| XSLT 3.0, XPath 3.1 | Saxon-HE 726,956 (MPL-2.0) | Saxon-PE/EE: extensions, streaming, schema-aware |
| XQuery database | BaseX 693,830 (BSD), eXist-db (LGPL) | MarkLogic 14,512 (Progress) |
| XSD 1.1 | xmlschema 476 (MIT), Xerces-J (Apache) | Saxon-EE |
| XSL-FO to PDF | Apache FOP 129 | Antenna House, RenderX XEP |
| Editor, debugger | VS Code 550 with XML extensions | oXygen XML Editor, Altova XMLSpy 106,997 |
| Browser XSLT 3.0 | (none open source) | SaxonJS 726,956 (free, proprietary licence) |
The open-source stack covers everything a data pipeline needs; the commercial products add convenience, streaming of huge documents (Saxon-EE), XSD 1.1 inside XSLT, and authoring tools. oXygen XML Editor, the common choice for hand-editing XML, Schematron and XSLT, lists a perpetual Professional licence with one year of maintenance at $942 or a subscription at $34 a month (USD, October 2026). Budget for the commercial pieces only where the free ones measurably fall short.