In my previous role at Adobe, I was the Senior SDK Technical Content lead for LiveCycle ES. In this role, I developed a lot of Java, .NET, and Flex apps that interacted with LiveCycle. The LiveCycle ES platform is still a powerful enterprise platform.
I have dig up some of my older community articles for the LiveCycle ES that are useful:
1 - Creating enterprise database components.
2 - Displaying LiveCycle ES process data in Flex graphs.
3 - Using Java servlets to invoke LiveCycle ES3 processes.
4 - Creating form rendering ASP.NET applications.
5 - Invoking web services using custom components.
By the way, you can use Adobe Experience Manager and LiveCycle ES as well. See this community article:
Integrating LiveCycle into Adobe CQ applications