I am considering using roundcube for messaging on a non-internet-connected LAN - which (I think) precludes using googlespell.
Are there any other approaches to spell-checking that could be (easily) integrated with round-cube?
You can change $rcmail_config['spellcheck_engine'] to 'pspell' in <RC root>/config/main.inc.php but that does require the pspell php extensions.