I’ve made a couple of steps forward with the Charming project:
1. I’ve added a new library for Windows Phone 8.0 and 8.1 Silverlight to provide a “Universal Apps” style ResourceLoader for Silverlight (.resx) resources. It currently supports the default AppResources string table only but this is enough in most cases to reduce your #ifdefs a little where you are sharing code between a Silverlight phone app and a Windows Store app. It could also be useful to help move an existing Silverlight app to the new runtime model in stages.
2. I’ve changed the license on the project to the MIT license which is even less restrictive than the previous Microsoft license. While this is currently showing on the project site it won’t be reflected in NuGet until each of the packages is updated.
3. I’m still looking into the Windows 10 SDKs to see which bits are still relevant going forwards. Despite the core Universal App Platform there are still different APIs on Phones and PCs where it might still be necessary to bridge the gap.