The "Install Ubuntu" icon can say "Install RELEASE" instead of "RELEASE" is never replaced with the specific string identifying a particular Ubuntu version. For example, a corrupted installation image for Ubuntu 12.04 LTS might say "RELEASE" instead of Ubuntu 12.04 LTS.
It seems this can also happen if there are "pieces" of the installer left over on an installed system.
So there are two general causes of this:
If Ubuntu is already installed:
If Ubuntu is already installed, and you're seeing an "Install RELEASE" icon in your dash, then:
- You don't have to do anything. It shouldn't be there.
- If you installed from installation media produced from a normal Ubuntu ISO image (rather than a modified image or an image for another OS), this is definitely a bug.
So, if Ubuntu is already installed, here's what to do:
You don't need "RELEASE." There is no such thing, it's remnants of the Ubuntu installer left over in the installed system. (Perhaps they were already there, and when you upgraded to a subsequent release, they somehow were shown. Or if you used a live CD/DVD/USB to upgrade, maybe that left them somehow.)
Don't continue trying to install it; if it did install something, that would actually be bad, because your system is already installed.
If the "Install RELEASE" icon appears in the launcher on the left side of the screen, you can simply remove the "Install RELEASE" icon from there. Just right-click it and click "Unpin."
If you installed from a normal installation ISO (as far as you know), you might want to report this as a bug. After reading that thoroughly, you'd start the bug reporting process by running
ubuntu-bug ubiquity (as the bug would be in the
ubiquity package). If that doesn't work, use other methods detailed in that guide.
You might be able to remove it and any other remnants of Ubuntu's installer that shouldn't be present in a fully installed system, by opening a Terminal window (Ctrl+Alt+T) and running
sudo apt-get remove ubiquity. If you're going to report the bug, it's best to do that first before performing this step.
In summary: If Ubuntu is already installed, you don't need to do anything, you shouldn't continue running "Install RELEASE," and you can even remove it from the launcher.
If you have not yet installed Ubuntu (and your computer didn't come with it installed):
If you are trying to install Ubuntu but you see an "Install RELEASE" option instead of "Install Ubuntu" or "Install Ubuntu 13.04" (or some other version), then you probably have bad installation media. It could have been created from a corrupted ISO image, or it could have become damaged.
So, MD5 test your ISO image, and check your CD/DVD or USB flash drive for defects. (This problem is quite different but it may have the same cause, so see my answer there.)
If you're using unofficial installation media, like something created for your company, or you're installing some Ubuntu-based operating system that is not an official derivative, then you'll have to get help with this from the provider of the installation media or the support resources for the OS you're using.
If your installation medium appears good and this still happens, please provide more details (by editing your question, plus you may want to comment here as well).