org.soyatec.eclipse4sl.core and org.soyatec.eclipse4sl.vex.silverlight currently declares dependencies on PDE in its MANIFEST.MF file. From analyzing the code, I'm not entirely convinced that this is really necessary.
The org.eclipse.eclipse4sl.vex.silverlight plug-in in particular actually has no references to PDE code anywhere. If you delete the Require-Bundle entry in the MANIFEST.MF file and save, the plug-in will continue to compile and function without any problems.
for org.eclipse.eclipse4sl.vex.silverlight, it is done