I want to start renting dedicated servers for counter strike 1.6
The problem is that some of my potential clients wants the players without a licence to be able to join on those servers. For this it's required to apply a patch known as "Dproto" - it can be found on a russian forum.

... i have emailed valve about this and they mentioned that it's against their Steam Subscriber Agreement. I know at lease one company that host these type of servers but valve didnt take any lawsuit against them...

Don't do it. You emailed Valve and asked them what they thought about you running pirate copies of their software - that tells me that hosting pirate servers is the last place you want to be.

The chances are that company isn't making enough money for steam to be bothered "yet".
Or they are in a area that makes it harder to take them to court.
either way just don't!

Don't do it. You emailed Valve and asked them what they thought about you running pirate copies of their software - that tells me that hosting pirate servers is the last place you want to be.

Just dont. Its against the Valve TOS. Why would they let you do that.