Sure looks interesting. It seems like a good idea for specific use cases, like for instance backup storage. The SQLite usage for the inode table is a neat hack. Implementation details here:
<a href="http:&#x2F;&#x2F;www.rath.org&#x2F;s3ql-docs&#x2F;impl_details.html" rel="nofollow">http:&#x2F;&#x2F;www.rath.org&#x2F;s3ql-docs&#x2F;impl_details.html</a>