MacFUSE is software that allows you to write arbitrary file systems as user-space programs. You can think of it as a library for easily developing Mac OS X file systems. Another crude way to look at this would be to think of MacFUSE as something that makes Mac OS X work like a microkernel for the purpose of writing/running file systems. MacFUSE has two major components: an in-kernel loadable file system and a user-space library (libfuse). The in-kernel file system is specific to Mac OS X and is not based on Linux FUSE. (Some of its code is based on the FreeBSD implementation of FUSE.) The user-space library (libfuse), which provides the developer-visible FUSE API, has numerous Mac OS X specific extensions and features.
With Mac OS X, you do not need to use such software. This function is part of Mac OS X. Follow the instructions in technical document 106282: "Mac OS X 10.0: Setup Assistant Does Not Accommodate DSL User Name and Password"
To take a screen shot with Mac OS X hold down the Command (cmd) key and the shift key and either the number 3 to take a shot of the whole screen or number 4 to change your pointer to cross-hairs that can be dragged across a section of the screen to capture just tat part. With the cmd+shift+4 option you can put your pointer over a window and press the space bar to capture that window,
In the Utilities folder which is in the Applications folder is software called Grab which does the same thing but also allows for a delayed capture which gives you ten seconds to arrange your screen before taking the shot.
You can't exactly edit pub files on a Mac, but you can convert the file to PDF.
You can either use OS X's built-in PDF viewer (Preview) or, in the case of other file types, download a dedicated reader from Barnes & Noble or Sony.