http://www.omegat.org/en/howtos/compatibility_deja_vu.html
The html has a link to:
http://www.atril.com/docs/DVX/InstructionsExternalView.pdf
But it seems broken. Probably the pdf has moved to:
http://www.atril.com/sites/default/files/InstructionsExternalView.pdf
...or
http://dvx.atril.com/docs/DVX/InstructionsExternalView.pdf