Before you go through this blob, I suggest you read my blog post "Your program license does not allow you to publish" to get an understanding about the Runtime Packages. 
 
Runtime packages are designed to help the distribution of extensions. You can generate Runtime packages that do not contain AL code. Runtime packages allow protecting the AL source code. 
 
The biggest advantage to me is that extension in a runtime package can be installed on a server that does not have a developer license. In other words, you can install the runtime extension to the production without changing the customer license to a developer license. 
The license is only checked on the server where the runtime package is generated. 
How to get the runtime packages
It is a must to install the extension into an on-premise instance to export the runtime package. next step is to connect to the instance through PowerShell and then download the runtime package. 

You can use "Get-NavAppRuntimePackage" PowerShell cmdlets do download the extension:
 Get-NAVAppRuntimePackage -ServerInstance DynamicsNAV -AppName 'Proseware SmartApp' -Version 2.3.4.500 -ExtensionPath 'Prosware SmartApp_2.3.4.500_runtime.app'  
Once you have the runtime extension you can use the Publish-NavApp and the Install-NAVApp PowerShell cmdlets to publish and install the extension. 
Limitations
Runtime package only works for on-premise installations and cannot be used with AppSource. Addition to that  debugging experience is very limited since the no source code is available 

Please provide your feedback with a comment. 
Thank you and Regards,
Tharanga Chandrasekara