Most users won't want to compile Jamulus from source as these scripts do. Usually, you should use the official Debian/Ubuntu repository as described on the Linux installation page on jamulus.io
In contrast, this repository is for scripts to allow unattended upgrades by compiling Jamulus from source. Usage examples would be to allow automatic upgrades for Raspberry Pi, server images or other systems without using the official repository to have full control over the produced binaries.