I don't think so. I thought the "spirit" was the opposite of that, that open source would let consumers of software avoid vendor lock-in or monopoly control of the software.

How are newcomers to know what the mystical "spirit of the agreement" is if it's not written down?

How do you detect that there isn't, in fact, a precise consensus over the "spirit of the agreement" if it's not written down?

That's how society generally runs on all scales, whether we are talking about the office fridge or about national law. Things generally start with very few explicit rules, and new rules get made when they are proven necessary.

"Guesswork" doesn't seem like a good way to do anything without stumbling into a lot of confusion and miscommunication.

But really I was referring to the process of how the laws are formed in the first place. A lot of the time they start out under-specified, and as abuses emerge we make more concrete laws using our new understanding. Of course the latter part usually leads to a lot of discussion and resistance because of the collateral damage any new law causes by being slightly broader than necessary. Which is a major reason many industries self-regulate in the attempt to make explicit laws unnecessary.