> A greenfield Java implementation with an MIT license would have been useful[2] for rendering TeX inside of my desktop Markdown editor[3]. Instead, I had to rename all the Java source files to abide by the NTSPL license terms (or GPLv2, which is viral).

The source files make it look like DANTE owns the copyright, so you could try asking them to relicence it. Both Philip Taylor and Hans Hagen were involved in the leadership of NTS, and both are still active, so if they are okay with it, then DANTE would hopefully agree to relicence it.