Serna uses "Hunspell" spell-checker (the same spell-checker is used in OpenOffice, LibreOffice and Mozilla Firefox). Only en_US dictionary is included into distribution, but on Linux and MacOS X platforms Serna will try to use system-installed Hunspell dictionaries too.
Additional dictionaries for many languages may be downloaded from http://wiki.services.openoffice.org/wiki/Dictionaries.
To install a new dictionary, unpack downloaded .zip dictionary file into the plugins/speller/hunspell folder.
Domain-specific dictionaries which extend primary dictionaries may be installed into plugins/speller/hunspell/extra folder (only .dic files, .aff file from primary dictionary will be used).
Serna keeps personal word lists in $HOME/.serna-<version>/serna-speller.<lang-code>.pwl files, in UTF-8 encoding.
It is possible to specify additional search paths for dictionaries by adding new <dict-dir> properties to the speller/hunspell section of Serna configuration.
Existing personal Aspell word-lists can be easily migrated to Hunspell by using Spell Checker Settings -> Import dialog (browse for .pws files in the $HOME/.serna-<version> folder).
It is still possible to use legacy Aspell spell-checker instead of Hunspell. To enable Aspell, please change speller/use property to hunspell in the config-template.xml, remove old Serna configuration from $HOME/.serna-<version> folder and restart Serna.
Serna uses unmodified GNU Aspell spell checker that is included under the GNU LGPL license (see ASPELL-COPYING in the installation directory). This implies that license terms are applicable to the spelling library aspell-*.*, located in the plugins/speller directory of the installation and to the files residing in plugins/speller/data files.
You can download sources for the library either from its official web site, or from the Syntext web site.
The Serna package includes the English word-list for Aspell, maintained by Kevin Atkinson, see copyright details in ASPELL-EN-COPYING in the plugins/speller/dict directory.