England and Wales permissive paths

If the footpaths are for the public to use there is not much different from a legal right of way. You can add an operator=* tag to the footpaths to show that these paths are operated by the local voluntary group.

Try adding the designation=permissive_footpath tag in the advanced tagging screen. See also the wiki page about the designation key.

The operator tag also mentioned in these answers is useful to say who it is that maintains them.

For footpaths that aren't designated as footpaths, bridleways, byways etc. I personally wouldn't use "designation" - I'd tag the access as accurately as possible (which might be "yes", "permissive" or perhaps something else), and if relevant add some sort of note explaining the situation.

Here is one example. see also here, which shows how people have mapped paths that are open for permissive access under the DEFRA scheme.

I did a search of the wiki for "permissive" here's a link to one example of tags http://wiki.openstreetmap.org/wiki/Trails In England permissive paths can be withdrawn by landowner so they are better than nothing but be wary of landowners who get paths classified as permissive that you know, are from years of use rights of way so they can then close them.