I'm making a simple JS game that needs a list of English dictionary words. Will I need to build the list myself, or is it possible to access the system's or browser's spell-check dictionary - or maybe there's another solution?
You can use Aspell English dictionary.
Aspell English dictionary is availabe at: ftp://ftp.gnu.org/gnu/aspell/dict/0index.html.
To dump world list from the Aspell dictionary checkout:
The command to dump English list of words should look something like:
aspell -d en dump master | aspell -l en expand > words.txt