THe FAQ makes it clear that prerelease software requiring an NDA is off-topic for the site. But not all pre-release software requires an NDA. Is pre-release software that doesn't require an NDA an allowable topic?
For example, Installing Windows 8 Preview on a Mac? was closed as off topic, but at http://msdn.microsoft.com/en-us/windows/apps/br229516, one can download the Windows 8 preview without any NDA.