In my opinion, all of these open source/free/open document signing tools are neat on paper (and technically fulfill the goal of being able to verify a document's chain-of-custody/signature provenance) - but won't take off in any meaningful way legally because there's no entity behind them taking the responsibility for accuracy and culpability.

DocuSign/Adobe/whomever is trust anchor, it's an entity you can sue or subpoena if something goes wrong. Someone who's actually on the hook for making sure whatever's signed is accurate and truthful (outside of the reputational risk of fraud completely obliterating any trust in your platform)...

No amount of cryptographic verification substitutes for having a legal person on the other end who can be held accountable for actually verifying the document was signed accurately/process was followed.