The article has since been updated to reflect this clarification. Apple's EULA for Snow Leopard allows the installation of one copy of OS X on one Apple-branded computer, while Snow Leopard Server allows additional copies of Mac OS X Server on the same computer, as long as you have licenses for each of these copies.
Editor's Note: Since this story was posted, Oracle has updated its Web site to clarify that VirtualBox is for use only with Snow Leopard Server.
