Pedigree Query

I'm not exactly sure which section to post this in, but it seems to qualify as a pedigree/breeding question.

I'm curious about the phrase "open lines", used in a quote from the Bloodhorse.com article about Americain standing at Swettenham in Australia -

"Americain is out of the Arazi mare America and has duplicated open lines to Plucky Liege, Blossom Time, and Sierra in a similar but slightly stronger genetic pattern to the recent English Derby (Eng-I) winner New Approach, who is one of the world's hottest young stallions," Kevin Bamford said.

I understand the "duplicated" part, but what exactly does the "open lines" part mean?

Here's a link to the full article, if you want to read more -
http://www.bloodhorse.com/horse-racing/articles/75471/americain-to-stand-at-swettenham-stud-in-2013

It's a good example of a rich neophyte owner trying to sound like he's knowledgeable about pedigrees. Americain is about as similar to New Approach as I am to Mr. Ed.

Guys like this are a prime target for the Nicksters, who prey on the pseudo--horseman who is looking for good advertising copy.

It may be a way of saying that the genetic pathway to Plucky Liege go through different individuals. Which is really the way to count inbreeding.