I notice that Atlassian is a proprietary limited company. How is that different than a U.S. corporation?

[Gary Weaver]

I always saw "Atlassian Pty Ltd." at the bottom of the Atlassian website, so I decided to look it up today and found that it stands for Atlassian Proprietary Limited, which I assume is the Australlian equivalent of a U.S. corporation. What is the difference between a Proprietary Limited Company and a U.S. corporation from Atlassian's standpoint (for those working in the U.S. or those that have to handle U.S. legal concerns for Atlassian)? Also, what are the legal complexities that Atlassian has had to hurdle by being a global business with offices around the world (i.e. with so many definitions of business and rules around business, what sort of things did Atlassian have to do to expand)?

[Joe Clark]

Here's the wikipedia article, but it's a bit scarce on details: http://en.wikipedia.org/wiki/Proprietary_company#Proprietary_limited_or_unlimited_company