NOTE: I have NOT tested if svn:externals works at all. I am only suspecting that it isn't working because the files are above the checkout folder.
My project uses a few "svn:externals" to folders that are a folder above the folder that I am checking out.
My other SVN clients are able to resolve this and pull in the external files/folders from the relative path above the checkout path.
OASVN is not creating the svn:externals folders.
Samsung Epic CM9 Ice Cream Sandwich