For whoever is interested, I've started a simple - but I hope useful - free and open source PropertyGrid project for WPF.

The source is available here: https://github.com/SoftFluent/SoftFluent.Windows and there is also a nuget package here: https://www.nuget.org/packages/SoftFluent.Windows.

It has no dependencies, but requires .NET 4 as it uses WPF's .NET 4 DataGrid class.