ShareWay IP is the only way to let a pre-X Mac's Personal File Sharing share files with a Tiger or Leopard system. These system's AppleShare client (through the "Connect to File Server" menu item) can only access AFP (AppleShare) servers that provide file service using TCP/IP. They do not support AFP over AppleTalk. ShareWay IP Personal Edition adds TCP/IP file sharing capability to any Mac OS machine running Mac OS 7.5.5 or later, letting that machine's files be accessed from Mac OS X.
Mac OS X sometimes even lists servers available over AppleTalk, assuming that it can connect to them via TCP/IP. Many times this is an incorrect assumption, since the "server" is not running ShareWay IP and is thus an AppleTalk-only server. In these cases, OS X will display an error message when you try to connect to the server, until you install ShareWay IP on the server machine.
ShareWay IP also lets other AppleTalk-only servers share files with a Mac OS X system. Servers like Windows NT and Novell Netware provide AFP support, but only over AppleTalk. ShareWay IP Standard and Professional Edition add TCP/IP file sharing capability to these and other AppleTalk-only AFP servers, letting those servers' files be accessed from Mac OS X. In these cases you run ShareWay IP on a gateway Macintosh.
Please send any additional questions you may have about ShareWay IP and Mac OS X to shareway@opendoor.com.