I enabled the spell checker in my config file, restarted the server, edited the Content Manager's rich editor and enabled server side spell checking. When I open an asset to edit it, I get a list of the libraries, but when I click to do a spell check a JS popup comes up saying...
"Please specify: spellchecker_rpc_url"
It looks like, on the tinyMCE side, that the spell checker plugin has been completely rewritten to use AJAX.
I'm working on this.
I made this a gazillion years ago. My guess is that TinyMCE changed API or something and that it broke. If necesarry I can have a look at it at the WUC (or hopefully sooner).
I've fixed this. The spellcheck plugin is now built into TinyMCE, but doesn't offer all of the features of the old plugin.
I couldn't see any good way to hook in the needed features, so I duplicated the plugin and modified it. I included a patch to aid with future maintenance.