Cycle all objects in that folder and publish them:
wftool = getToolByName(folder, 'portal_workflow')
for child in folder.objectValues():
wftool.doActionFor(child, 'publish')
Question
How can I programmatically change the state of all objects in a folder to 'published'? All are default objects of Plone 4 as Link, Page, Document, and so.
Solution
Cycle all objects in that folder and publish them:
wftool = getToolByName(folder, 'portal_workflow')
for child in folder.objectValues():
wftool.doActionFor(child, 'publish')