Recently we had to pull the freeware application Grid from the App Store. Grid allows you to position windows using your keyboard and an on-screen grid. Unfortunately Apple’s strict sandboxing rules no longer allow third-party apps access to e.g. the Accessibility kit which Grid needs to move the windows.
Grid’s author, Rob Rix, has now made the app open-source and published it to GitHub. Feel free to download the source code and participate in its development.