Thank you for your internet in Telerik AppManager.
Yes, unfortunately, you cannot distribute Windows Phone apps outside of the Windows App Store without first obtaining and signing your apps with the Enterprise certificate. This rule is imposed by Microsoft and we cannot go around it.
The package url is a direct link to the app's package - APK, IPA, XAP or APPX. It is a simple feature that lets you get the file of the app you have in AppManager. The idea is that you might want to download the package and save or use it in some other place too.
I hope this information is useful. Let me know if you have any questions.