The reason I wrote it this way is: on the landing page, a search engine visitor is… a search engine visitor. One of those 80% that will go away right now because in a glance they won’t find what they were looking for, and hopefully go away with an ad click.

Now, if they visit a second page, they become a LOT more than just a one time search engine visitor. They got interested by your CONTENT, so why pollute their read with ads that they won’t click anyway?

This said, there is a much better way to do what you’re wanting than modify my plugin.

1) Create a custom function that either sets a cookie for SE visitors or checks if the cookie exists
Something like:
function cookie_or_SE() {
if (wp_ozh_wsa_is_fromsearchengine())
[set the cookie];
if ([the cookie])
return true;
return false;
}
2) In your ad rules, use an advanced rule like:
if (cookie_or_SE()) then {display}