Download james-jpa-guice-3.8.2.zip from the download page and deflate it.
An usual compilation using maven of this Git repository content will produce two artifacts into server/container/guice/jpa-guice/target directory:
You can for example run in the base of this git repository:
mvn clean install
To run james, you have to create a directory containing required configuration files.
James requires the configuration to be in a subfolder of working directory that is called conf. You can get a sample directory for configuration from server/apps/jpa-app/sample-configuration. You might need to adapt it to your needs.
Edit the configuration to match your needs.
You also need to generate a keystore in your conf folder with the following command:
$ keytool -genkey -alias james -keyalg RSA -keystore conf/keystore
Once everything is set up, you just have to run the jar with:
$ java -javaagent:james-server-jpa-guice.lib/openjpa-3.2.0.jar \
-Dlogback.configurationFile=conf/logback.xml \
-Djdk.tls.ephemeralDHKeySize=2048 \
-Dworking.directory=. \
-jar james-server-jpa-app.jar