..actually, I think that Archive::Tar is a Pure Perl module, but it uses (though does not depend upon) another module for gzip compression which is binary and requires compilation.

Indeed it does: Compress::Zlib. But development of this module is independendent of that of Archive::Tar.

Comparing Activestate's version with the most recent one on CPAN, you can see that they're both the same version: 1.16. So there's no problem about that.

Update: Ah, damned: the above URL to Activestate's package again doesn't include a port for Win32. The other, older repository does, but is only at version 1.08.