For the simplest and quickest installation type,

make install

This will install Adun into $HOME/GNUstep. 
After starting Adun for the first time (type 'openapp UL') you can 
do the following to install the provided plugins, 

cd Adun/Plugins 
make

Thats it. For a more detailed install guide see diana.imim.es/Adun
