PL

Dont put Valve or Dota 2 Logo.

You can put some form of disclaimer on the tag (if you do sell).

Or if you're really scared of lawsuits, write to a valve employee.

Valve may be anal about it but usually as long as you're not marketing it as in affiliation with valve then it would be owkay.

But I suggest a simple email and say its a one-off thing or small time thing.

come give us some samples man.