Strangely, but true, you cannot install from the the original site, or run it. So how to install and run UNetBootin?
Installing UNetbootin via PPA
sudo add-apt-repository ppa:gezakovacs/ppa sudo apt-get update sudo apt-get install unetbootin
In Ubuntu <18.04, we can directly install UNetbootin with single command
sudo apt-get install unetbootin
But UNetbootin is unavailable from the standard Ubuntu >= 18.04 repositories, due to requiring now-deprecated dependencies (e.g., gksu, kdesudo). The standard UNetbootin PPA, which explicitly supports Ubuntu >= 18.04, should be leveraged instead.
As commented in your question by Web-E , you should just add the executable permission to the file downloaded from SourceForge, then you are able to run it (no installation needed, btw). I had the same problem and that comment gave me the solution, without the need to add the ppa.
If you don't want to use terminal, you can right-click the file
unetbootin-linux-585, select "properties", go to "permissions" and then tick "allow execution of the file as a program" (or something like that, i don't have an english-language o.s.).
As suggested in the comment below, here's a little how-to about making a file executable:
To make the file executable via terminal (and we are here supposing you downloaded that file using a browser like Firefox or Opera), you only have to go to the folder where the file resides, right-click on the folder and select "Open terminal here". When you have the terminal shell, don't forget to run
to make sure the file is really here, and to check permissions. You should see something like
-rw-r--r-- 1 name name 4478124 lug 11 15:28 unetbootin-linux-585
which means you have to add execution permissions on it. How you do it? Simply typing:
chmod +x unetbootin-linux-585
(don't forget to use Tab to autocomplete the long unetbootin name :P).
Now, checking again the file with
ls -l should give the following result:
-rwxr-xr-x 1 name name 4478124 lug 11 15:28 unetbootin-linux-585
This means that the program became executable, so just type:
to run the application.
Hope everything is clear.
Installing UNetBootin appears to be pretty simple, you can either install it via the source from sourceforge.net or using PPA, easy one will be PPA
sudo apt-add-repository ppa:n-muench/programs-ppa sudo apt-get update sudo apt-get install unetbootin
And to use UNetbootin, there is basically two different option, one is to install downloading the distribution as mentioned by the UNetbootin itself and next is to select Disk Image and choose ISO files.
See full tutorial on How to install and use UNetbootin in Ubuntu 14.04?