I have posted an additional "Bonus" modification at ThreadsAddons.com for subscribers to the Search Engine Optimization Mod. It is called "Forum Header Inserts" and allows you to create header inserts (and thus forum specific META tags) for each forum.
It's free for existing subscribers of the Search Engine Optimization Mod - supplied as a "bonus". It's available for download in the Search Engine Optimization Mod Members Area at
www.threadsaddons.com