I’m volunteering for a few organisations and communities now. Typically IP and NDA contracts are antagonistic to FLOSSers (organisation claims anything related to them under either the IP or confidentiality clauses) and require you to be an employee receiving payment to be fully in effect, which is not the relationship of multiple independent people working together for each other for free in an organic way, maintaining, sharing, or assigning resources while respecting privacy of privileged information and data.
I’ve done up the following alternatives, let me know your feedback:
Mutual patent waiver implicitly achieved via the imaginary clause.
Liability waiver is too involved for this, as same for an employee contract, if a contribution caused harm accidentally, it is probably forgiven, however if the harm was intended, then it is probably followed with law, so omitting a liability waiver leaves action up to the instance.