Looking at the rules for double and jotungrip off of www.d20pfsrd.com, jotungrip allows me to "weild a two-handed weapon in one hand with a -2 penalty on attack rolls while doing so." Note that the weapon is still two handed but "is treated as a one-handed weapon when determining the effect of Power Attack, Strength bonus to hit, and the like," meaning all bonuses. Using a double weapon means that I can use it to "fight as if fighting with a two-handed weapon" while incurring "all the normal attack penalties associated with fighting with two weapons." Note that the weapons are STILL two-handed, but will subtract an additional -2 to attack rolls. However, I can still "wield one end of the weapon two-handed (which I'm not because the weapon, though two-handed, is in ONE hand) but cannot use the weapon as a double weapon when wielded this way (which I'm STILL NOT, for previous stated reason)." Therefore, I should be able to use it as a double weapon because I am not wielding it two-handed, but with a -4 to attack rolls without bonuses. This will only work as long as I do not apply bonuses to my attack rolls.