chore: update license fields in package.json (#1298)

Sets license for all node.js packages to `GPL-2.0-or-later`

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Chores**
- Simplified license compliance verification by removing legacy script
logic.
- Updated licensing terms across components to GPL-2.0-or-later for
broader compatibility.
- **Documentation**
- Revised setup instructions to indicate that the use of the Just build
tool is now optional.
- **New Features**
- Added fallback support in the build automation tool to ensure smoother
operations when targets are missing.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

plugin/package.json

@@ -14,7 +14,7 @@
     "zx": "^8.3.2"
   },
   "type": "module",
-  "license": "GPL-2.0-only",
+  "license": "GPL-2.0-or-later",
   "scripts": {
     "// Build scripts": "",
     "build": "pnpm run build:txz && pnpm run build:plugin && ./scripts/output-local-url.sh",