npm installs it automatically with @afterpack/core on Linux x64. Don't install it directly. Install the main package instead:
npm install @afterpack/core
Most people use the CLI (npx afterpack) or a framework plugin. Start with the quickstart or the CLI reference.
License
Free for any use, including commercial and CI, with no limits, and the output is yours. You can't redistribute the binary on its own, build a competing obfuscation product or service on it, or reverse engineer it. See the AfterPack Engine License.