Re: OOC : Relaxation room
What languages you gain are clearly explained on page 140:
One homeworld language at a native level, the one you are raised with, per species or nationality (English for most of you, Polish for Kaspar, Norse for Hilda, etc.)
All SGC recruits who weren't raised speaking English (say Kaspar, Hilda, and Vasandra), gain English for free at a fluent level. The book says "most SGC recruits are American, and therefore all who do not speak English as a native gain English as a fluent language for free."
A number of bonus languages equal to your Intelligence bonus. It says the "bonus native languages may be either homeworld or alien languages". Hence, Hilda learned Goa'uld, even though it's not a homeworld language.
"Native" languages are those you speak sounding like a native, more or less. "Fluent" languages are those you can speak confidently, but with an accent or unnatural sentence structures or word choices. "Homeworld" languages are those spoken on your homeworld, and are handled by the Languages skill. "Alien" or "Xeno" languages are those spoken off your world, and are handled by the Xeno-Languages skill.