I'll try to remember what I did...
a) You need the spell.js, spell.css, SpellCheck.aspx, and dictionary files from the spell checker in your .NET app. I created a directory called spell and put them there.
b) Pages using the spell checker need to include the spell.js Javascript code.
c) Finally, I added a spell check button to the editor that calls (note the use of my spell directory in the path):
checkSpelling(controlToCheck, 'spell/SpellCheck.aspx');
d) I modified the SpellCheck.aspx that came with NET Spell to set this.SpellChecker.IgnoreHtml = true in the Page_Load event.
I believe that's all there was to it.
- Alan