Found another walking site using OSM, e.g. http://www.gmap-pedometer.com/?r=6828602 shows OSM as a base layer.
Unfortunately, there's little/no OSM attribution, only Google :-(
Comment from iandees on 11 May 2017 at 22:59
I suggest you use their contact or forum pages to politely ask them to add proper attribution.
Comment from ndm on 11 May 2017 at 23:05
No easy way to contact them without creating an account on their website -- or possibly twitter.