Our Live System is running on 3.9.3.
And i also managed to import OpenFire 3.9.3 Sources Files form the zip file offered on the main page into Intellij as project(with some try and failers for configure the project).
But i used the same steps to develope the plugins.
I only took the 3.10 because all plugins are included with newest source files.
UPDATE:
JUST for Testing i downloaded openfire 3.9.3 and try to import as project. And my created plugin jar files have this *.jar.pack ending now.
But i know that i mange to create clean jar files fith the 3.9.3. source files.
So the problem is, how you import this project. But i dont remember the right steps for correct import of the project.
UPDATE2:
Found out that if your change the build.xml
from
<property name="pack200.enabled" value="true"/>
to
<property name="pack200.enabled" value="false"/>
will disbale the pack function. So that the plugins have clean jars inside.