The Hunspell spell checker is open source and has LGPL license. The format of the Hunspell spell dictionary is supported by Mozilla, OpenOffice and the Chrome browser. Oxygen XML Developer plugin comes with the following built-in dictionaries for the Hunspell checker:
There is one dictionary for each language-country variant combination. If you cannot find a Hunspell dictionary that is already built for your language you can build such a dictionary. First you need a list of correct words which you want to check in your documents. You build a dictionary from this list following these instructions.