This is incorrect. Canonical formerly used a (non-joint) copyright assignment agreement, which was widely criticized. It later sponsored the Harmony project which was an unsuccessful effort to popularize a standardized suite of contributor agreements. When the Harmony agreements were released in 2011, Canonical began using one of the Harmony CLAs. It doesn't stipulate copyright assignment; rather, the contributor grants Canonical a broad copyright license that is similar in effect to copyright assignment except that the contributor
retains copyright ownership of the contribution. It is not dissimilar in policy to the widely-used Apache model of CLAs. I'm a strong critic of CLAs generally, particularly these types, but they ought to be described accurately. The effect of use of such CLAs by entities that will (by employment of a majority of developers, say) hold copyright over much of a relevant codebase is that you have little pieces of code that are owned by outside contributors but licensed in under
maximally broad terms which basically give the inbound entity the ability to do whatever they want with the code, short of assigning copyright in it.

> Even RedHat requires you to sign a similar CLA in order to accept contributions for Fedora, 389 Directory Server (LDAP), etc.

No (with some legacy use of Apache-style CLAs basically confined to some JBoss projects and gradually being dismantled).

I've been Red Hat's open source lawyer since 2008 so I think I can speak authoritatively on this. Red Hat does not use a similar CLA for contributions to Fedora (though at least nominally it used an Apache-style CLA prior to 2010). Since 2010 Fedora account holders agree to the Fedora Project Contributor Agreement (http://fedoraproject.org/wiki/Legal:Fedora_Project_Contribut...) which is a simple agreement that says code is licensed by default under the MIT license (and content under CC BY-SA) unless the contributor indicates otherwise. 389 basically followed the Fedora approach for reasons best understood as historical inertia (by coincidence I noticed last night there is some incorrect information
about this on the 389 website).

Red Hat starts up tons of open source projects, and most of them do not require contributor agreements. When I got to Red Hat in 2008 this was already the case, if only because of the nature of Red Hat's culture at the time. But the company was on the verge of applying a uniform (Apache-style) CLA requirement across all Red Hat-maintained projects -- much like so many companies do today. I very soon realized how problematic that would be and I think one of my big accomplishments was not only to stop that from happening but also to reverse it (the trend for that set of projects that used CLAs in the past has been to get rid of them), and to formulate a strong legal-policy basis for doing so, maybe best recorded in my two-part critique of the Harmony contributor agreement suite in 2011: http://opensource.com/law/11/7/trouble-harmony-part-1 .

So please do not use Red Hat as evidence of support for use of broad contributee-friendly contributor agreements. Red Hat has been the leading company, maybe the only company, articulating an alternative viewpoint.

[Edited to fix formatting and to tone down initial scorn slightly]
[Edited to acknowledge JBoss situation]
[Edited to note Harmony agreements unsuccessful in that few use them]