There's something weird there. The instructions doesn't mention sudo, and I run the server just fine without it. If you need to use sudo to run it, I imagine there's something strange going on for you. When you run things with sudo, you don't get the same environment variables and whatnot, so that could perhaps be why you're having issues with the builder.
My best guess (and it absolutely is a guess) is that you should download a fresh bx4buildserver and start over. If you get the same error - make sure to not sudo - you probably need to remove some keystore somewhere. But, like I wrote, it's just a guess. I do know for sure though that sudo isn't needed.