I knew there wasn't 'a file' to modify and, bam!, paid app support. I was asking about the specific file that is modified *before building a new kernel*. Every file I looked at, in what I assume is the correct location for the kernel in the source directory, had a note at the top telling the reader not to modify the file, as it was auto-generated. I wanted to know the location of the .config file. Another member of the forum, in a different thread, mentioned he had done so, and the specific items he had changed in the .config file, but he didn't mention the *location* of the file...
I'll take a look at the link you provided. Thanks!
I succeeded in building the KitKat image by using the provided Ubuntu build VM. It runs very smoothly and (mostly) without problems.
In my build I addressed several issues of the original image, including the necessary modifications to the kernel to be able to install paid apps. The next step will be to build the tun device into the kernel to be able to use VPN apps like vpnc.
Everything I built including a short documentation is available in my github repository at https://github.com/tkurbad/wandboard
@michrech: To enable paid apps, you can't just change some file and be set. You have to modify the kernel configuration and compile a new kernel. However, a prebuilt kernel can now be found in my github repository (s.a.)