The validation process for C++ applications is built into the yearly membership fee, which is at this time free. This is the best time to get into ATOM app development.
Thank you for your query.
C and C++ apps do not require to be digtally signed yet as it is with AIR apps. It is also a requirement from Adobe to have AIR applications digitally signed. There are 4 certification authorities where you can get your code signing from. Some of them may be arounfd the $500 while the others are cheaper. Please find more information on this link: http://appdeveloper.intel.com/en-us/article/adobe-air-packaging-guide-atom-developer-program-submissions
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