We open-sourced our startup (
https://github.com/hummingbird-me/hummingbird) and I think it was fairly successful.
Personally I feel that the git history is useful so I would prefer not to release just a snapshot. Would be better to rewrite history to remove anything that should not be there.
We ended up using the Apache v2 license, mainly because it requires granting copyright and patent licenses from contributors without getting them to sign a CLA.
In terms of having a successful open source project the most critical thing is to attract contributors. Some easy things you can do towards this end:
1. Simplify your installation process. I found that for Hummingbird the biggest barrier to new contributors right now is our complicated installation, and I am working on getting something working using Docker/Fig.
2. Identify some easy potential contributions and add them to your issue tracker. When I want to contribute to a project the first thing I do is look for easy issues, and a lot of projects make this easy by specifically tagging issues that would be easy for new contributors to tackle.
3. Like arielm said, documentation is very important. Make sure you have a well written README, CONTRIBUTING etc.