2 site about same contents?

it is not clearly to me

[dolcevita]

It is not clearly to me about TOS
"domains with substantially duplicate content"

Does it mean that i can;t have example 2 or 3 sites about antivirus or 2 or 3 sites security and firewalls?
Or it means only if you have 2 exactly same sites with different domains?

Second "Do not participate in link schemes designed to increase your site's ranking or PageRank"

I hope that this does not mean that you can't place friendly links (a couple) on your site.

[dirkji]

Duplicate content means more or less identical content, not content relating to the same subject.

Placing links on your site is no problem, Google is referring to link farms.