If this really supports Snow Leopard, that is a great contribution. Kudos and applause for the developer. Apple has long abandoned updates to Safari to run on 10.6, while lots of third party browsers continue to support it. This lack of continued support, is probably one reason to avoid using Safari.
However, it seems that there are separate downloads for separate Leopard and Snow Leopard versions. So, one wonders if maybe there ought not be a separate MacUpdate page for the Snow Leopard version?
Currently, the MacUpdate download link seems to give one a Leopard only download. http://sourceforge.net/projects/leopard-webkit/files/ has the various OS specific installers. All of the downloads in the 600, 538 folders, say they are for Leopard Power PC.
However, the 537 folder does have a mixture of Leopard and Snow Leopard installers.