OS X Yosemite Beta 1: Troubleshooting Download Issue
I managed to download OS X Yosemite Beta 1 in the early Thursday morning before AppleSeed site went offline. Later that day I heard reports that some people were having trouble downloading the installer. I later confirmed that I also did have trouble downloading the installer on my other Mac.
Sometimes on Friday Morning, I still had trouble downloading the installer on that Mac. Interestingly, at the same I could download the installer on my primary MacBook Pro.
There is a possibility that it has soothing to do with Mac App Store cache.
Should you have trouble downloading OS X Yosemite Beta 1, try clearing up your Mac App Store cache.