Linux users have WINE if they need it, but OS X users pretty much need a commercial package I believe. As Raa said most of them are WinRAR archives so you can extract them with unrar under Linux and rename them with a .rar extension for OS X and StuffIt Expander can handle the rest. Something like TBP is a true Windows installer though so you would need Windows or a Windows emulator to get access to that. TBP is going to move the cross-platform installer (java based), and that was planned for 3.3, but it just didn't work out that way. The next release of TBP will be cross-platform, even if I have to distribute the damn thing myself.
As far as VP archives go, those are accessable in Linux and OS X as well. In CVS (or the source tarballs) you can type "make tools" and get a set of tools, including cfilearchiver and cfileextractor. These are CLI based tools, which is rather alien to many OS X users, but they aren't difficult to use. cfilearchiver will create a VP archive out of a directory structure and cfileextractor will extract files from a VP archive (or just list the files).
