GNU tar (the compiled binary that runs with a constant and fairly small memory footprint) is available for windows and is basically native on all unix/linux, so why not use that? (e.g. via a system call)
Comment on Re: Lightweight, Platform-Independant Tar
While GNU tar might very well build on every Unix, it is reasonably common for it to either not be installed, or to not be called tar. It's often called gtar instead.