You can embedded a Mailchimp form on your Givecloud site.
1.Create the form in Mailchimp. Here is there help article:
2.Copy the embed code provided by Mailchimp
3.Paste in the 'Code' tab of the page builder where you would like the form to populate
4.Save the page
Note: all information collected through this embedded form will be sent to Mailchimp, nothing will populate or documented in Givecloud.