You're looking in the right place, the main executable should be right there.
I've installed that same version of Builder recently on my Ubuntu 14.04 laptop and it worked just fine. My guess is that your downloaded file is corrupt and the actual ejecutable wasn't able to created.
The other posibility may be that you don't have suffucient permission to install in the directory you did. If you installed in your home directory (which is where my installation ended up), it should have worked fine.
Still, I'd put my money on a corrupt downloaded installer. if at any point during your download it was interrupted and you had to "resume" it, throw it away and try again.