Routes developed at national/regional level (typically, they are part of a local cycle network) but not signed with EuroVelo signs yet - I think these should be mapped as EuroVelo but with some kind of tag to say that they are not signed as such
Routes “under development” or “at the planning stage”, meaning that these routes have been selected to become EuroVelo and the region/locality may have plans to improve their infrastructure, but they can contain dangerous sections - we can decide that these routes should not be mapped in OSM but in some countries, they are the “best available solution” for cyclists and it’s still interesting information
As long as they’re tagged as such, that’s fine - I’m not going to get all “deletionist” about what belongs in OSM and what doesn’t.
I’m mostly worried about situations where the (undeveloped) route is currently mapped along a busy road, or an unimproved rocky trail. Routers often take official cycle route status as an assurance of some minimum quality, and obviously an undeveloped route doesn’t come with this assurance. If a router sends someone along a very busy road, and claims it’s a EuroVelo route, that’s not good for the cyclist, the router author or indeed EuroVelo/ECF!
(Proposed cycle routes have been mapped in the UK since cycle route mapping first began in OSM, mostly using state=proposed on the relation - you can see this if you zoom into OpenCycleMap, for example here.)
We are going to make a proposal to the NECC for a common open source license. Do you know which licenses make it easy for OSM? If we go for a license of the type ODC-by, with required attribution of www.EuroVelo.com, would that make things complicated on OSM? I would guess yes, since the required attribution changes when we put tracks on OSM?
ODC-By is good. Generally you just need to accept that a credit to www.eurovelo.com at Contributors - OpenStreetMap Wiki (which is linked from the OpenStreetMap link customarily placed on-map) will suffice - the EuroVelo credit won’t appear directly on the map when downstream users show an OSM map.