Open Office, Numbers app and Pages app (the default applications for working with .docx and .xlsx on MAC) are unable to open documents exported with RadWordsProcessing and RadSpreadProcessing. 

The issue is in the relationships parts, relationship element. The Target attribute can be either a URI (Target="/word/theme/theme1.xml") or a relative reference (Target="theme/theme1.xml") as stated in Ecma Office Open XML Part 2 - Open Packaging Conventions.  RadWordsProcessing and RadSpreadProcessing use URI, which the applications for MAC (Numbers and Pages) and OpenOffice are unable to interpret, despite them being allowed by the specification.

The fix will be available in our official release Q2 2016.