It can get a little confusing when Adobe starts rebranding things.
Adobe LiveCycle has gone out of life and is no longer supported by Adobe. The specific desktop tool I believe that you are referring to still exists but has been rebranded as part of the Adobe Experience Manger Forms solution (AEM Forms).
When it comes to OSGI versus JEE they are how the solution Adobe Experience Manager Forms solution is installed. A lot of the same functionality exists in both the OSGI and JEE versions including the desktop Forms Designer tool. One of the key differences between the OSGI and JEE is how form workflows are handled. Within the JEE version it leverage the desktop tool Workbench which in OSGI they have a different workflow system. Note you do need to be OSGI to move to the cloud, so keep that in mind!
All that said for the Forms Designer tool you can use it either installation setup of the Adobe Experience Manager Forms solution. Check out this link to learn more about Adobe Experience Manager Forms Designer.
https://www.linkedin.com/smart-links/AQHNv4erEkZeRQ/672020f6-26a9-4be1-a986-34894818ec6c