You will need the original game to make use of Operation: Omega Dawn- it is not a stand-alone game. It is scheduled to be coming out soon, according to most reports. Have a read of our news area to find some more out about it.
While I do agree somewhat with the sentiment of not wanting to pay for the extras that is pretty much the standard modus operandi with the downloadable games these days. The cost of the booster pack will be very reasonable- only $7.99 US. That should translate to a mere 4 pounds for you folks in the UK (roughly). Not a bad deal for what's in the package (a new dropship vehicle, a night time battlefield with 6 different layouts and 5 bonus layouts for the original maps that will allow you to use the dropship).