It’s possible, but not easy. You can download old planet files, but you’d have to extract the area you’re interested in, then render it, then compare it with what’s currently there.

Remember that you’d only be comparing what had been mapped then versus now – it’s not necessarily a record of how an area itself has changed.

OSM should be thankful for their contribution in the first place

I am, and I'd be even more grateful if they'd allow their contributions to continue to be used. Unfortunately some people have got the idea that the licence change is some kind of conspiracy, or a stitch-up, and others are actively promoting this idea.

OSMF has chosen a legally and morally responsible way of going about the licence change. It has asked every single contributor for their individual permission, and given them a choice. Many projects have used legal sleight-of-hand (Wikipedia) or require full copyright assignment for all your contributions (GNU).

Talk of OSMF "deleting" data is nothing of the sort. It's simply staying within the law, and respecting mappers' wishes. I wouldn't call that ungrateful.

The practical situation is that the vast majority of useful contributors have agreed to the new CTs and licence. The small pockets of data that remain are by and large replaceable from other sources. As others have already said, those sources should be used rather than just deleting and recreating the same objects. The end result will look very similar, but that's because they're both models of a single reality, and they're meant to be almost identical.

Please believe this: OpenStreetMap remains an open, freely-licenced project, where anyone's constructive contributions are welcome.

If someone wants to set up a Twitter feed pointing to the Announce archives they're welcome to, but it's not something we're planning to do ourselves.

The feed chilly points out is run by another OSMer, but I think their idea is to report lots of OSM-related news, where the announce list is intended to be just announcements of events that will affect the whole community on an operational level -- new software, downtime, that sort of thing.

Remember that the "approvals" process isn't official, and that "Any tags you like" trumps any vote.