Chris here…
What about something like:
[i]Hey everyone,
As these forums get busier and busier as the new ThunderCats series gets closer and closer, we’re looking for a couple of volunteers to help out with moderating our forums! 
What we’re basically looking for are a couple of folks who’d be willing to help us deal with things like spam posts on the forums, threads accidentally posted in the wrong forum, and things like that. In particular it would be really good to have a couple more moderators based in the US, as most of this site’s team members are now based in Europe and so there are time periods where we’re all offline and thus things like spam posts are sitting unattended for several hours. 
If anyone would be interested in taking on this role, please could you post up in this thread letting us know that you’re interested, what sort of times you’re able to be online, and what timezone you’re in. 
There are many factors we’ll be considering when deciding who to pick out of the candidates available (including things like timezones, etc.), so if you don’t end up getting selected, please don’t take it personally - we’re sure it will be a difficult decision for us to pick just a couple of people! 
And just to add, although I’m sure you guys will have figured this out already, unfortunately any work done for this site (including that of those of us on the team) is all unpaid and done by fans for the benefit of other fans, so sadly there’s no salary, even though we think all you guys are worth your weight in gold! 
Looking forward to hearing from you all!
[/i]
…Something like that? I think it covers all the bases, makes clear what needs making clear, but doesn’t sound too “heavy”. I don’t want to post it up until I hear back from you guys, if you can think of anything I’ve missed out, LMK and I’ll add it in or change it! 
Take care… 