Guests limit to single board

[Admin]

What's the limit number of single-board guests that can join your board without being billed?

[Felix]

Single board guests are never billed. You can add as many guests as Trello will allow. Currently the limit for members per board is quite high (over 1000).

Any guests (non-workspace members) that are on more than one board (multi-board guests) are billable.

[Admin]

Dear Trello community,

I'm introducing Trello as a project kindly provide me with all of your knowledge about its server, storage, security & backup with evidence to be sure that it's safe from an IT perspective 

Best regards,

HW