TMX Editor is a Java Swing GUI built for working with files supporting the TMX localization standard.
I found the application yesterday and tried to open an OmegaT tmx file just to see what the tool was able to do and, well, nothing happened. I sent a mail to Matthew Gagne, the project manager and received this answer a few minutes ago:
It seems as if this problem relates to the version of the TMX standard that is implemented currently.
http://www.lisa.org/standards/tmx/ lists 1.4b as being the official revision level. The editor, however implements the newest TMX 2.0 draft standard using the locale4j library. This was a decision made when we began localization of our other projects here. Unfortunately there seems to be compatibility issues between the two TMX formats (1.4b vs 2.0).
Since TMX 2.0 is unlikely to be in widespread use before a while, Matthew also mentioned that he'd love if Java developers could join the project to work on backward compatibility with the current TMX version.
locale4j is the library that is at the core of TMX Editor. It currently works only with TMX 2.0 data.
Both TMX Editor and locale4j are licensed under the Mozilla 1.1 License, which is a Free Software License not compatible with the GPL.
File2XLIFF4j is quite another beast: File2XLIFF4j is a java based library for converting files to the XLIFF standard. The overview shows that the library is not exactly for the normal translator, but it is still important to know that such conversion libraries exist.
Interesting to see that the overview author, Weldon Whipple, has a "lingotek" email.
File2XLIFF4j is licensed under the GPL.