JNVDL http://jnvdl.sf.net
Open-source Java implementation written from scratch
Supports many schemas through Java 1.5 validation API
oNVDL http://www.oxygenxml.com/onvdl.html
Open-source Java implementation written from scratch
Supports many schemas through Java 1.5 validation API
SnRNV http://www.asahi-net.or.jp/~eb2m-mrt/nvdl/SnRNV-1.0.zip
Open-source Java implementation written from scratch
Supports many schemas through Java 1.5 validation API
enovdl
Open-source Mono/.NET implementation