There currently is not mechanism for that as code sharing is automatically provided by all the users using the same LK installation (e.g. WebWerkstatt or Lively Web). At least that is the idea.
For sharing kernel code, we use git commits either from local installations or the Lively Web.
One way you could backup and share code (a backup is automatically done through the wiki feature btw.), you can - depending on the way you are developing - place all the code in a module that resembles a JS file (say http://lively-web.org/users/CarlosCrosetti/project.js - which makes it the users.CarlosCrosetti.project module).
If you are developing with Parts, I currently cannot think of a way of achieving the same (the PartsBin is the place for sharing and reuse and it can be referenced from different LK installations, versioning is provided automatically). Though Parts are also just a combination of HTML, JSON and MetaInfo files (see http://lively-web.org/PartsBin/Fun - Elephant for example).
I hope this provides you with some solution for what you are thinking about.