Guild Wars 2

I did a lvl72 renown quest which have a base karma reward of 615.

http://wiki.guildwars2.com/wiki/Renown_Heart

With 15% karama amulet, and 15% karma from guild +6% from achievement, my final karama reward is 836.

But I have a birthday booster on. So apparently, birthday booster don’t boost karma gain?

Apparently yes. The wiki also confirms what you experienced: http://wiki.guildwars2.com/wiki/Birthday_Booster .

Did they just made it soulbound? They were account bound back in December before I took a break from game.

Mine still say Account-bound on Acquire. The Birthday Gifts are Soul-bound on Acquire, though.