NOTE: this is not intended to be a ready-to-use product. Please think of this as a reference implementation. I just put it up here to test various ideas floating around this thread, nothing more.

Requires Python 3.4+. pipsi is recommended:

pipsi install --python python3 git+https://github.com/iamale/lepton.git#egg=lepton-vm
# or:
pip3 install git+https://github.com/iamale/lepton.git#egg=lepton-vm

A Lepton application is a folder with a package.json in root. This is a generic package.json, but in the engines object, at least one particle (runtime) must be specified. Also, a lepton object should be there, containing a run command. Particle binaries are passed as $VARIABLE-like strings (uppercase and s/-/_/g).

{
  "name": "atom",
  "productName": "Atom",
  "version": "1.10.0",
  "description": "A hackable text editor for the 21st Century.",
  "engines": {
    "electron": "1.2.5"
  },
  "lepton": {
    "run": "$ELECTRON ."
  }
}

Lepton supports SemVer and the advanced range syntax:

{
  "engines": {
    "electron": "1.x",
    "node": ">=0.10.3 <0.12",
    "python": "^3.4.3",
    "bash": "*"
  }
}

All available particles are hosted here. For now, it's only Electron, but more will be added soon (nw.js? node?)

A particle is a folder with runtime and a particle.json file, which is just like a package.json (we use a different name so that it won't be confused with generic packages). It must specify a path to the binary in the main field (this is what will be passed to the lepton.run in the packages).

{
  "name": "electron",
  "productName": "Electron",
  "version": "1.2.5",
  "main": "./electron",
  "os": ["linux"],
  "cpu": ["x64"]
}