A lot of open source folks are going to be very skeptical, rightly so, of this group of players.
> ... to find, fix, and responsibly disclose vulnerabilities in critical open source software ...
How this is implemented is going to be key. Are they going to contribute through (a) existing channels, pull requests etc. or (b) are they going to fork the projects under the guise of 'security' or (c) offer bug bounties or (d) contribute financially?
Approach (a) brings the community along. (b) alienates the community, splits resources, and in the long term will likely cause many open-source projects to die. (c) has potential but timing and speed can be unfavorable for critical bugs, and doesn't mesh with 'responsible disclosure'. (d) can be ineffective for critical bugs unless paired with support for maintainers, which can be incredibly helpful for the opensource ecosystem.