The only way to download iOS 5 Beta 6 legally is to be a registered Apple developer. A developer registration is available from Apple’s developer website for $99 per year (if you don’t belong to a company) and won’t only give you access to pre-release seeds of iOS, it will also let you access exclusive developer-oriented tools and documentation. While this subscription is indeed mostly aimed at developers, it’s almost essential for any serious iOS enthusiast to own one. Who knows, you might actually become a developer one day.