The comments here are pretty stupid. Apple allowing access to source code is a basic thing. Microsoft also allows access to source code to large business partners.
Personnal example, we needed Outlook not to go through American servers, because of the size of our business, they allowed making a server elsewhere (Canada). It cost a lot. But if you believe that your internal data and the data of your clients is confidential, you can't just say yes to external software, or cloud services. You need to be able to make an audit and see what is going on. Costs a lot? You bet. But what happens if your customers lose confidence in you? How much cost to your reputation if your data is hacked?
Ask Sony.