Wrap this jar using an exe wrapper or a bash script on Linux & I think you are ready to go, you can also wrap the executable file together with other assets using an installer to build a zip file or exe installer :
That what I have used for my ANT projects, you can use those with gradle too.
I donot know what else then ? , May be use the installer in something like steam, may be, I haven’t published a full maintainable software before(except for google play) , but I see Mythruna , Lightspeed Frontier and the jumping jack may be good examples for you.
About copyright & other infringements , usually most of the advanced installers softwares have a wizard for those like ‘Do you accept our liscence ?’ dialogs & so on , you can configure what suites you.
If you’re planning on using steam you dont need an installer at all. You just lay the project out however it needs to be on the installed computer and then use steam pipe to upload that to steam. Then steam puts everything in that layout on the end users machine.