The OWB 11.2.0.3 clients for Windows and Linux 64-bit clients are now on OTN for download at the link below;
http://www.oracle.com/technetwork/developer-tools/warehouse/downloads/index.html
You should now see a line for the Oracle Warehouse Builder 11g Release 2 (11.2.0.3.0) Standalone Software and links for Linux and Windows 64-bit downloads.
The software can also be downloaded from Oracle Support as described in this post.