If I share a board with a guest, who has a free account, can they copy the board into their own account so they have access to edit it?
Yes, they can copy the board. However, note that when a board is copied, the following are not copied - comments, card activity or archived cards. https://support.atlassian.com/trello/docs/copying-cards-lists-or-boards/
It looks like you're new here. Sign in or register to get started.