You cannot download Serato DJ Lite 1.0.5 from the official website anymore—it redirects to the latest version. Here is how to get it:

This guide is maintained by DJs who refuse to throw away perfectly good hardware. Mac OS X 10.6.8 is unsupported, unpatched, and glorious. Serato DJ Lite may have moved on, but in the right configuration, it still beats modern bloated software on cheap plastic laptops.

For a machine running Snow Leopard, you would need to look into :

Snow Leopard loves to throttle CPU speed to save power. When Serato DJ Lite needs a sudden boost (e.g., loading a track while looping), the CPU ramps up late, causing a dropout.