There is a Seamonkey package in SliTaz.
I did add the settings for spell checking dictionary but nothing happens.
1/ how to do it?
2/ as Mozilla uses hunspell and provides some hunspell dictionaries, how to make them accessible for other app's esp. LibreOffice ( https://en.wikipedia.org/wiki/Hunspell ). Lyx would also use hunspell today ( http://wiki.lyx.org/Devel/Hunspell ) better than apell.