Since this is a democratic model of governing a company, is there a way to create a coalition to slowly overthrow the governing members and take over the treasury and ownership of the project? How would this then affect the actual ownership of BetterMeans - are all current members also equal shareholders?
Yes. It would be totally possible to overtthrow the governing members of bettermeans.
However, shares are not tied to your membership. Ownership is based on contribution, and cannot be taken away from you. Just wether or not your votes are binding.