Is Speed Metal Remastered Map free?

Yes. Speed Metal Remastered Map is released under CC-BY-SA-4.0 and costs nothing. Neither it nor Zero-K has any paid content.

What do I need to run Speed Metal Remastered Map?

Zero-K, which is itself free. Speed Metal Remastered Map is an add-on and will not run standalone.

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

Roughly 12 MB, on top of the base Zero-K installation.

Yes. The source is published at github.com/ZeroK-RTS/Zero-K under CC-BY-SA-4.0.

Speed Metal Remastered Map — Free Zero-K Mod · PlayBound