If you have a checklist that you'd like to share with the world, perhaps a template you think other people could benefit from, you can do that.
On the checklists page, find the checklist you wish to share. For that checklist, you'll find the Publish action in the More Actions button.
You'll then be on a page that has a link to the published checklist, which you can share with anyone. Simply share that URL and someone can copy your checklist into their Manifestly account.
Note: If you're looking to share a checklist with someone in order for them to work on it, then you'll need to invite them to a checklist run.