Developers have confirmed that iOS 5 solves a slowdown for home screen web apps. A confirmation Thursday showed that Web.app, the gateway for web apps operating outside of Safari, has the same "dynamic-codesigning" privilege as Safari and can use the Nitro JavaScript engine key to the speed-up in iOS 4.3. Regular apps that need a web view don't get the speed, but here the issue is with security as it could act like a workaround.
