<meta name="googlebot" content="index,follow">
<meta name="msnbot" content="index,follow">
These can be dropped from your header. If your site is open to the public, Google and Bing pretty much already see your site as something available for indexing. How nice.
Your keywords dont need spaces after the commas. You can use spaces, but they are not needed.
Your description tag is good. Meta descriptions can be any length, but search engines generally truncate snippets longer than 160 characters. It is best to keep meta descriptions between 150 and 160 characters
re "powered by" - IIRC, in admin, go to the "Languages" section and perform a search for those words. You'll find a language item where you can place your forum's slogan, if you choose.
