"The “Corresponding Source” for a work in object code form means all the source code needed to generate, install, and (for an executable work) run the object code and to modify the work, including scripts to control those activities."
I get that it's really hard to make money as an open source company. (That's why I am one of your paying customers.)
The exclusion you are putting on your SDK seems very similar to that of the "bitkeeper" version control software used for the Linux kernel for a short time. Look how that turned out.