You can't exactly edit pub files on a Mac, but you can convert the file to PDF.
It all depends on what you are downloading. Sometimes it is best to leave it at the default for what the mac thinks it should open the download in. If it is a text document, open it with Word.
no
The Darwin kernel of Mac OS X is open source, as are many other parts of the OS. (See links below) but Mac OS X itself is not open source and Apple only allows it to run on Apple hardware.
Is MacOS an open source system? No.
To open Windows media files with QuickTime on Mac OS X use the free Flip4Mac plug in (See links below).
Classic Mac OS is closed source. Mac OS X is closed source as well, but many libraries and applications within it are open source, e.g. XNU the kernel is open source, and Darwin the underlying UNIX operating system was open source.
The main OS for Mac can be found on a Mac when it is switched on. The current main OS is called Mac OS X.
You can't unless it's been converted to the Windows version. The Mac OS and Windows OS are two completely different computer languages.
Firstly, Im assuming you are referring to a window in which you save or open a document in mac os, since you haven't specified. In mac os, the "browse" button to view your file hierarchy in a "save" or "open" is a single arrow pointing downwards next to the text box in which you name the file. Clicking this does not open a new window, but expands the existing window and places your file hierarchy in the middle. From here you can chose the exact location to save or from which load a file.
Perhaps the Mac does not meet the requirements to run FrostWire on a Mac which are: Mac OS X 10.5 or later Java 1.6 or later.
I have a Mac OS X but I know Mac OS is a computer made by the brand/company, Apple.
Applications may not open because they do not find the operating system they were expecting. Both the latest versions of PaintBrush and iPaint require Mac OS X 10.5 (Leopard) while the latest version of GIMP requires Mac OS X 10.6 (Snow Leopard). There are older versions of the software available that support older versions of the Mac OS such as 10.4 (Tiger).