@Stanislav Makrushin - The Business Plan supports "Guests", which let's you add users to your boards without having to add them as team members. You can can even control access per user, e.g., John can edit, but Jane can only view. This is different than Visitor access where anyone with the link can access the board. More on the Guests feature here:

https://help.miro.com/hc/en-us/articles/360021415119-Collaboration-with-guests

Restricting copying of board content

While you will never be able to stop someone from sharing their Miro account credentials, you can (and should) set your board's permissions to only allow the board owner/co-owner the ability to copy content/duplicate the board. This will ensure that your clients cannot copy/export anything from the board, or duplicate the entire board - more on this here:

https://help.miro.com/hc/en-us/articles/360018350399-How-to-allow-or-restrict-copying-and-exporting-boards-and-content

Well, the problem is that when you send this email invitation to your guest, what this guest may end up doing - having his email published on Instagram, for example, with any generic easy password, and 100 users would login to my Miro board - and this is exactly what restricts my monetization efforts. My idea is to make my materials visible only to desired users. Not only doesn’t Miro support One device = One login = One user policy, but also there’s no way to choose the preferred method of authorization for my clients. I’ve paid for the upgrade to business plan, and the only thing the “SSO” feature allows you to do - is to let people with corporate email domains be exlusively logged into my board. I guess I will have to create 100 gmail accounts, registered on my name, and when I decide to provide exclusive access to my MIRO board to my clients, I will just send them one of those 100 email addresses with unique passwords, and apparently will work my way around this problem