There are far more problems than NDA's and IP ownership going on here. Moreover - I don't think the failure to sign an NDA would change the nature or 'who owns

There are far more problems than NDA's and IP ownership going on here. Moreover - I don't think the failure to sign an NDA would change the nature or 'who owns what' for the most part (unless it governed paid work, which most NDA's don't - they are simply 'non disclosures' i.e. 'keep this a secret' type docs). Finally - it's hard to imagine a contract that specifies that the code that consultants write is 'owned' by the company - when payments are not made. A consultant could require that the code does not belong to the company until it's paid for, legally. More pragmatically - all legalities aside - if a company is not paying for services rendered, it's easy enough to withhold the code. If the company wants to move forward - they can pay for it. The last thing a startup wants to do is start a big legal process and go through courts to 'get access to their code'. In the end all these problems are not due to legal documents, they are due to people not being paid for services as per their agreement.