Just run ./make.sh Libo_PlantUML
The extension is currently dependent on you having plantuml.jar like HOME/plantuml/plantuml.jar
On Linux this is /users/[user]/plantuml/plantuml.jar On Windows this is in C:\Users[user]\Documents\plantuml\plantuml.jar
This initial version is a core transformation from the original macro by Poul Bondo (e-mail: pba@mailme.dk) here: http://sourceforge.net/projects/plantuml/files/plantuml.odt/download