I tried to put all necessary information in the wiki, but this continues to be a source of questions, and I reckon current Map situation is undesirable:
2) it doesn’t seem to be another obvious candidate for default, choosing an alternative free server without previous agreement will likely produce the same result sooner or later, free services with ample usage quotas are increasingly difficult to find.
3) It will be possible to use a tile server with registration required s.t. OpenCycleMap without a key so the map displays a warning and the user can register to have their own quota.
Ideas are welcome.