can a free user interact with custom fields if someone in the workgroup has a standard?

[Idr]

If I upgrade to a standard account to create cards with Custom fields can a free user interact with those custom fields that I invite to my board?

[Alex Waite]

Hey @Idr, I think first I should explain how subscriptions work in Trello. 

All boards created in Trello need to sit in a workspace. Upgrading a Workspace is the primary way of upgrading to a paid plan in Trello, and free workspaces can only have a maximum of ten boards open at a time. When you upgrade to Standard or Premium, all users that are considered billable within your workspace will go towards your monthly or annual bill.

Billable users in Standard and Premium are the following:

• Users that have been added directly to the upgraded workspace
• Multi-board guests: users that have been added to two or more boards in the upgraded workspace

Single-board guests - users that have been added to one board in the workspace - are not considered billable users. You can read more about how billing works with Standard and Premium here.

If you add someone to a board in a Standard workspace, they can access the Custom Fields on that board. If you then add them to more than one board in the workspace, they'll become a billable user.