I think that you roughly could divide the sources used by OSM mappers in England**** England** into 3:
1. [On-the-ground GPS traces](//wiki.openstreetmap.org/wiki/Recording_GPS_tracks)
2. [Old out-of-copyright maps](//wiki.openstreetmap.org/wiki/Out-of-copyright_maps)
3. Newer sources such as [OS OpenData StreetView](//wiki.openstreetmap.org/wiki/Ordnance_Survey_Opendata) and [Bing imagery](//wiki.openstreetmap.org/wiki/Bing_aerial_imagery).
Going back a few years, there weren't many of (1) and (3) didn't exist yet, so footpaths then tended to be based on mostly (1) with some people drawing in "potential paths" from sources such as the "New Popular Edition" maps (2). Looking at the area that I think that you may be talking about, many of the paths there were originally added to OSM 4 or more years ago, and given the original mappers of a couple of examples, I'd suspect they were mostly from survey (one very prolific and active on-the-ground surveyor), but with a bit of guesswork too (a couple of other less-active mappers).
Since that time the availability of more more accurate GPS traces and newer data sources (that allow the sanity checking of GPS traces, and vice versa) has meant that it's been possible to map footpaths much more accurately. That's happening in many places in the UK; you may very well be the person to do it for your part of it.
In addition to Richard's legal comments one reason why I wouldn't consider a rights-of-way import particularly useful is it merely reflects what footpaths a local council thinks that it has and where they go, not what actually exists. Certainly there are some just northeast of the main town to your southwest where what's on the ground didn't match the council's data (the last time that I looked).
<small>**and possibly elsewhere in mainland UK.</small>