Review for Vietnamese Dictionary by Pinky!
Rated 5 out of 5 stars
2.0.2.138 works fine on FX 6.0 (Windows 7).
BTW, I'll be glad if .oxt (for LibreOffice or OoO) also has both New and Old dictionaries because the feature is really helpful.
To create your own collections, you must have a Mozilla Add-ons account.