According to the SGOS 6.3 release notes, Websense on-box is no longer supported and will not work. The Content Filtering database will be set to None and there is no way to switch it back to Websense.
Websense has removed official support for ProxySG and many others but they have not changed anything to prevent third parties from integrating with them.
In other words, SGOS 6.3 works fine with Websense off-box v7.6 and v7.7, but you must use ICAP integration rather than Websense onbox database integration. The GUI configuration for WISP (WBSN proprietary integration protocol), has been removed.
For more details on how to configure ICAP in Websense off-box, please refer to article below:
Note: In SGOS 6.4 Websense off-box support will be completely removed