The free DLC, which is the Car Mini-Album and Entity Pack, looks as if you would have had to post in the Sound Shapes birthday thread in order to receive it by Monday August 12th. Maybe there'll be another gift waiting when Sound Shapes turns two.
I did post in the thread the same day it was posted on the blog. I even went back to make sure it posted. I bought all the other DLC the same day except this one, and would have bought it too when it was on sale had it not had the thread to post "Happy Birthday" to receive it for free.