What a shame you impose such a barrier to entry - you'd think you'd be happy people want to develop for your products. I don't want to upload or sell anything, I just want access to the C SDK for a project I'm working on. Now I have to wait a week or more just to get access to an SDK?
I'd be quicker now reverse engineering the .skp file format than waiting for access to an API in a language that I'll still have to port to something more modern i.e. C# - I mean C? Really? Is it 1990?