Is Gemini Gold Full Speech & Radio Pack free?

Yes. Gemini Gold Full Speech & Radio Pack is released under Community Add-on / Fair Use and costs nothing. Neither it nor Privateer Gemini Gold has any paid content.

What do I need to run Gemini Gold Full Speech & Radio Pack?

Privateer Gemini Gold, which is itself free. Gemini Gold Full Speech & Radio Pack is an add-on and will not run standalone.

How do I install Gemini Gold Full Speech & Radio Pack?

The PlayBound Launcher installs it in one click from Privateer Gemini Gold's mods list. You can also install it by hand — full steps are on this page.