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I have tagged as "dubious" the statement that "most data covered by Crown Copyright is now under the new Open Government Licence". The source cited  does not support this claim. It says that the license applies "where the relevant rights owner [...] make it expressly available" under it – i.e. it is still limited to the initiative of each individual public body, and to those publications that are explicitly marked with the license. If this is now true for a majority of publications, we'll need a separate source for it. Fut.Perf.☼ 07:42, 2 February 2012 (UTC)
OK, this is a little complicated, but I will try to clarify this (rather complex) situation:
Crown Copyright is a legal existence (under the Copyright, Designs and Patents Act 1988 § 163 that exists automatically for any work "made by Her Majesty or by an officer or servant of the Crown in the course of his duties". Things cannot be transferred into Crown Copyright or out of it - if a non-Crown status individual creates a work, it will never be Crown Copyright.
Crown Copyright is not the same as normal "civilian" copyright. For example, it lasts for a different amount of time - creation plus 125 years for unpublished items, creation plus 50 years for published ones.
These created a transactional open re-use licensing system for all documents published by public bodies in the UK. Though public bodies could say no (and did), or charge at cost-recovery levels with some limited restrictions, in general they said yes for free re-use - but there were very few requests made, as PSI licensing was seen as slow (and gave public bodies opaque grounds to refuse).
It was "improved" a couple of years later with a system for online application for already-cleared PSI works (generally called the "PSI Click-Use licensing scheme"), where you could apply and get automatic written approval for re-use, but still take-up was poor (and thus harming the economy and being generally rather out-of-date).
So, over a period of a few years and culminating in 2010, The National Archives revoked the PSI "Click-Use" licensing model, and replaced it with the Open Government Licence. Specifically, this was done by TNA's Controller of Her Majesty's Stationery Office who (per her Letters Patent) is "Printer to Her Majesty of all Acts of Parliament and holder of all copyrights in Crown works" (my emphasis), so the line of "where the relevant rights owner [...] make it expressly available" refers to The National Archives, not individual departments - see this release that covers all Crown Copyright (except items covered by letters of delegation or those of the Scottish Parliament). This took place for Note that information published via data.gov.uk since September 2009 was licensed under the OGL (though at the time we called it the "data.gov.uk re-use licence" because final negotiations hadn't taken place).
The OGL has four main improvements: it is non-transactional (so, like Creative Commons, you didn't have to ask); it is much clearer language (so people aren't confused or scarred off from using it commercially), it is compatible with Creative Commons Attribution 3.0 un-ported (so you can combine it with other works without needing a lawyer and/or individual permission) whilst definitely being legally enforceable in all three of the UK's jurisdictions, and most importantly, it covers vast swathes of the UK's public sector information in one relatively simple regime that explicitly encourages re-use.
However, there are some issues with departments correctly reflecting the changed nature of Crown Copyright in their published works. This is especially true of some of the smaller organisations that may have missed the letters from TNA that went out around Whitehall in 2010 (and frankly, rewording a copyright and re-use notice is of minor importance at a time of reducing budgets, so those of us who care passionately about copyright have to muddle-through). I'd encourage anyone with concerns about the OGL nature of a UK Crown work to assume good faith, and if that's not enough for you,
Some specific points where this article is seriously inaccurate:
[...] public bodies can now opt to publish their Crown Copyright material under this license.
No; regulated public bodies with Crown status, other than a few with delegated authority, have no choice. If it is a Crown work and is published, it is under OGL (except for the Royal crests). Some non-Crown bodies (like local authorities) have adopted the OGL for convenience, but that's a distinct use-case and it's confusing to the reader to elide them.
Crown Copyright is the default copyright applied to all government department published documents.
No; it's is not a default, it's a state of being that is either true or not. Government departments don't get a choice. (Though it is waived in a few cases, departments don't get a choice here either.) Words here that are wrong include "default", "applied", "department", "published", and "documents". :-)
Also, there's no mention of any data releases since mid-2010 even though there's been loads see e.g.this. The section on "Data holders" confusingly covers three bodies that have letters of delegation alongside a fourth that holds commercial data (Transport Direct doesn't own the data it provides, it buys it from the private sector), and yet doesn't talk about any of the ones covered by the OGL or any of the data that's been released and for what purposes it's been used.
Of course, as acting head of data.gov.uk (2009-11) I clearly have a conflict of interest with this article's topic, so have never edited it. Please feel free to improve it, though. It really needs some love.