This is not a fair assessment and I think it sidesteps the point.
"This is very admirable and I appreciate the desire to help, but I can't stress enough how dangerous this is."
Indicating that 'medical equipment requires specialization' is not a special insight that most people are going to miss.
Assuming that the product will be designed by those who lack credibility or that such equipment might not be of sufficient quality of design, construction, or that it may be misused is unwarranted.
'Open source' encryption and other systems are behind the entire world's financial systems, it has integrity partly because it's 'open source'. It's not designed by fools, and just because jokers and everyone else can 'fork and do something' doesn't mean it will be implemented anywhere that matters. Obviously regulations, security, risk etc. play a role 'where it matters'.
Any kind of medical equipment development is going to require some kind of oversight, regulatory approvals, and special manufacture, but this is all feasible within the concept of 'open source'. There are plenty of highly credible and knowledgeable people, possibly even those who have worked on 'closed source' ventilators can possibly contribute.
Sheppard through some kind of regulatory process, manufacturing setup, and possibly deployment and training, it's not infeasible at all that something like this could help.
Even the availability of high-quality, unlicensed equipment designs, with parts pre-designed for manufacture and ready to be made by qualified entities ... could feasibly make all the difference in the world.
For example, once a design is complete and approved, the medical wing of a poor country, or possibly an NGO could facilitate the actual manufacture and distribution to medical staff in various places.
There are massive margins (bordering on criminal) in medical equipment and supplies these days, hospital beds now cost more than automobiles (!), it's high time there was an open approach to such issues.
I can absolutely see medical researchers and PhD's at universities, teaming with Engineers, MDs, and manufacture/supply chain specialists to produce this kind of stuff.
Obviously there's a limit to complexity here, but I hope they figure out not only ventilators, by any number of other kinds of gear.
Though odds are it will fail, it's not a bad idea, it's a great idea.