Star Trek Online free-to-play information is out and about in FAQ form and everything. Despite it's free to playness, there are tiers of membership.Yes, you guessed it, one of the tiers isn't free to play at all.
There are two (very Xbox Live'ish) levels: Gold and Silver.
Gold costs $14.99 - well, actually it says, "$14.99 Monthly (or Lifetime)" but the (or Lifetime thing doesn't mean $14.99 for your lifetime). Unlike Silver, your 'Energy Credit Storage Limit' is, confusingly, unlimited. You get three character slots not two.
Full FAQ is here. The
Gold vs Silver matrix is here.Beware though "As Star Trek Online's free-to-play effort is very much still in development, please be aware that the information provided here is subject to change pending user feedback and closed beta testing."