(What I'm about to ask isn't meant to "rock the boat" in any way. It is mean to understand the legality of public data.)
I started a discussion about sliproad problems and the legality of Google data came up. Ever since, I’ve been thinking about the use of Google data on OSM. For all intensive purposes, it’s very easy to retrieve roadside data just by driving down the road or (like using Bing in JOSM) using alternative map sources. As for road signs, they are free for drivers to observe and take note of. As such, what is the legality in regards to retrieving publicly accessible data to be used in a publicly accessible way (especially since OSM is open-source and community driven)?
Obviously, we don’t want to mess with grey areas. But, that should be easy to avoid (unless the government makes that complicated, which wouldn’t surprise me).
The legallity is in the fact that Google spent money to buy data, or paid people to get those data (the google cars). Simply the fact that road signs, traffic signs, speed limits, or even the roads themselves, might be visible for all, does it make it allowed to copy that data from others.
You now mention Google maps, but why not "steal" from navteq or TomTom or TeleAtlas who spend lots and lots of time and money to make their maps as complete as possible.
It's not the fact that the data is there, it is the fact that others put commercial time and money into it to collect it. Unlike OSM which is communitiy driven and open source.
"It's not the fact that the data is there, it is the fact that others put commercial time and money into it to collect it."
Which would make it a very grey area that OSM would need to tread lightly. Point taken. Plus, even if it was a matter of just getting through some red tape, it doesn’t look like much is donated to that:
If you use one of the web browser based edit tools or josm for example, there is a big statement that you are not allowed to copy data from other sources unless it is specificially and clearly licensed as some form of open data. More and more address data becomes in the public domain. Some governments even see it as their duty to do so. Denmark has all address data in OSM and it's done and maintained by the Danish government. In the Netherlands the address and houses data (BAG) is completely open and after deliberation with the OSM "advisory board" a team of 15 volunteers, including me, used a josm java extension to import all that.
There is a Dutch website and a German website that is completely driven by volunteer(s) that photograph all motorway signs, and making that publicly available. I also used that for the Netherlands and Germany to help complete exit signs in OSM based apps.
On the other hand: If you use Google or one of the other commercial solutions they all state that you are not allowed to copy blahblahblah...
So the grey area is not that grey. It is simply a matter of checking which data is allowed to be used, and in case of doubt: consult the owner(s).