One option is to install the system dependencies only in the Docker image. The ol3 developer would need to manually run `npm install` (to install local Node deps) and `build.py serve` in the container.

Steps:

```
$ docker pull htulipe/ol3
$ docker run -i -p 127.0.0.1:8000:8000 -p 9810:9810 -v <path-to-ol3-dir>:/workspace:rw -t htulipe/ol3
root@1234:/tmp# cd /workspace
root@1234:/workspace# python -m SimpleHTTPServer &
root@1234:/workspace# ./build.py serve
```

I know it's more work for the user but it makes things more explicit.

If possible SimpleHTTPServer (or similar) could be started automatically at container start time. But I think build serve should be run manually by the ol3 developer.