WriteableBitmapEx project is now 6 years old and times have changed since all began. It all started with Silverlight and more XAML flavors were added over time until all XAML flavors were supported including Windows Phone, WPF, WinRT Windows Store XAML, (Windows 10) UWP and still Silverlight.
The version control system and open source services landscape has changed as well and the CodePlex infrastructure has not been too reliable recently. That's why I finally took the time to move the WriteableBitmapEx source code from CodePlex' SVN bridge to Git and make it available on GitHub: https://github.com/teichgraf/WriteableBitmapEx
Additionally was the open source license changed from Ms-PL to MIT which should simplify the usage as well. See the Codeplex Issue Tracker for a list of features that will be added in the future. Please use the GitHub Issues functionality to add new issues which are not already reported. Of course the latest binaries will continue to be distributed via NuGet.