Where can I download OS Snow Leopard from for free ?

It isn't and never was available as a free download. If you want to instal Snow Leopard on an old Mac you will need to buy the 10.6 installer from somewhere like eBay.

The updates to Snow Leopard 10.6 are available online as a single "combo" update from Apple: Mac OS X 10.6.8 Update Combo v1.1

DianaAlSadi Said:

"Where can I download OS Snow Leopard from for free ?"

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It is Not Free:

As a friend for an installation disk? It costs money to install it. You can get the installer off of Amazon.