I don't know what kind of license you prefer. For an English Dictionary, the Princeton WordNet program and datafiles are essentially BSD/MIT licensed. I haven't looked for LGPL libs with dictionaries.
This is not in the plans, but if there is a free and ready to use library it can be included or used as an add-on like mathjax. In my opinion this feature will be used very infrequently tough.
On my mac,
$ port info enchant aspell ispell
enchant @1.6.0 (textproc, devel)
Variants: universal
Description: On the surface, Enchant appears to be a generic spell
checking library. You can request dictionaries from it,
ask if a word is correctly spelled, get corrections for a
misspelled word, etc. but all it really does is to provide
a uniform wrapper over several popular spell checking
libraries including aspell, ispell and AppleSpell.
Homepage: http://www.abisource.com/enchant/
Build Dependencies: pkgconfig
Library Dependencies: glib2, aspell, hunspell
Platforms: darwin
License: unknown
Maintainers: anant@kix.in
--
aspell @0.60.6, Revision 3 (textproc)
Variants: nls, [+]nonls, universal
Description: Aspell is a spell checker designed to eventually replace
ispell. Aspell's main feature is that it does a much
better job of coming up with possible suggestions than
ispell.
Homepage: http://aspell.net/
Library Dependencies: gettext, texinfo
Platforms: darwin
License: unknown
Maintainers: openmaintainer@macports.org, jochen@macports.org
--
ispell @3.3.02, Revision 2 (textproc, spelling)
Variants: universal
Description: International Ispell is an interactive spell-checking
program for Unix which supports a large number of European
languages.
Homepage: http://ficus-www.cs.ucla.edu/geoff/ispell.html
Library Dependencies: ncurses
Platforms: darwin, freebsd
License: unknown
Maintainers: nomaintainer@macports.org
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