**The bonus language granted by the Tongues curse is added to the languages you *know*, not the languages you can *choose to know by virtue of high intelligence.*** Here's why:

> You apply your character's Intelligence modifier to:
>
> - The number of bonus languages your character knows at the start of the game."

Note the wording: Bonus languages are languages your character *knows* at the start of the game, not a list of languages they could *potentially* know. Here's another quote, this time from the races section of the PRD:

> **Languages:** Dwarves begin play speaking Common and Dwarven. Dwarves with high Intelligence scores can choose from the following: Giant, Gnome, Goblin, Orc, Terran, and Undercommon.

The reason why this quote is significant? Those languages *aren't* described as "bonus languages." Again, this is because "bonus languages" are languages a character *knows* as a bonus of having high intelligence, *not* languages they could *potentially* know.

Incidentally, if you don't gain the language, it's not really a bonus. That'd be like calling "elf" a "bonus race" for your dwarf character because it's an option you *could* have taken.