Yes, that's right - Moodle accounts could be linked to Project MoodleNet accounts. Apologies if the metaphors didn't work!
To answer your other questions:
Could you expand on what would mean having social networking with other teachers from their Moodle instance?
Project MoodleNet will be a resource-centric social network, meaning that conversation / ratings / tagging is focused on resources. As such, it's valuable to surface this within Moodle instances where teachers and instructional designers spend a lot of their time.
And what do you mean by having better security and reduced costs in Moodle hosting?
People often forget their passwords, so being able to login via Project MoodleNet (if the sysadmin turns that feature on) should add an extra layer of security. In terms of reducing costs, it makes little sense to have unversioned resources in thousands of Moodle instances. So there's an opportunity to host this in a distributed way that reduces the individual instance hosting burden. Think of something like IPFS
I don't know in other countries but normally here teachers also have the role of "instructional designers", and in my case also sysadmin ;)
Absolutely. It's important for planning to separate out the roles, but we're committed to helping educators no matter the size of their Moodle instances, nor the number of roles they have within that instance!
Thanks for your questions - keep them coming