The unregistered add-in is a fully functioning program that offers the basic WordStar navigation keystroke set (the WordStar Diamond) plus its ^Q accelerators and some menu customisations. The keystroke set is much more limited than the commands available in the registered version.
I recommend that you use WinZip, but you can use any archive program that supports the Zip file format, including the oroginal DOS program pkzip, or the built-in compressed folder support in recent versions of Microsoft Windows.
Can installing Microsoft Word templates and add-ins that have macros be risky? Yes, it can. The WordStar Command Emulator program contains macros to enable it to work and you must allow these macros to run if the program is to provide you with WordStar commands.
The WordStar Command Emulator program is Shareware. Registration of the program entitles you to free minor upgrades, and support. Major upgrades may require a further registration fee. See the full pricing details.