if i'm on the iphone enterprise developer program for companies with >500 employees, do i still need to publish my app on the app store for clients to install the app?
If you do not intend to publish apps to the App Store, then don't. The iPhone Enterprise Developer Program is designed not to allow you to publish apps to the App Store. For that you need to also enroll in the standard program.
From Apple Developer's FAQ for the enterprise program:
If your company is enrolled in the Enterprise Program but would also like to distribute your application(s) to customers via the App Store, you will need to enroll in the iPhone Developer Program as an Individual or as a Company.
Just to clarify - the enterprise developer program allows you to build apps so that you do not need to register the devices in advance. However, you have to make sure that the apps you build are only used by employees, contractors, and "customers" (in very special situations). For more information check out the updated article "Apple iOS Enterprise Developer Program Summary" http://www.apperian.com/technote/Apple_iOS_Enterprise_Developer_Program
The iOS Developer Enterprise Program is now open to all companies - see http://developer.apple.com/programs/ios/enterprise/ - they removed the 500+ employee limit. This will definitely help companies that want to roll out internal "in-house" apps.
来源：https://stackoverflow.com/questions/3059741/publish-apps-for-iphone-enterprise-developer-program