Ask HN: Considerations for open sourcing a startup's code?

I am a cofounder at a small startup (http://devver.net) that will be shutting down soon.

We hate to see our work completely disappear. We are currently looking for a company to purchase our code but we're also considering open-sourcing parts of our code base.

We have investors and we're aware that "giving away" the code they paid to develop will not be very enticing, but if we spend our own time to do the prep work (and if we can show that the process is low-risk), they may prefer that to the code simply disappearing.

Does anyone have experience open-sourcing a previously closed-source code base, especially in a startup? Any advice, considerations, success/horror stories, or ideas would be appreciated.