Apple Allowing Non-Mac Developers to Download OS X Betas
Apple today launched a program where non-Mac developers can download and use betas of OS X. This is not just for OS X 10.9.3, it's going to be for all betas of OS X. You do need an Apple Developer ID, but a normal Apple ID will work.
Once you download the Mac Beta Updater you will be able to update to the latest beta within the updates tab of the Mac App Store. Apple does, however, want you to give them some feedback. You can do so using their feedback assistant. You can learn more about the program and enroll your Mac here.