In these particular cases I would expect there would be no assignment of copyright (however I would assume you're right about trademarks).

Despite the fact that there most likely is some transfer of intellectual property contemplated here, I do think the term "donation" is a little odd when describing stewardship transfer of open source projects to nonprofits -- though it's fairly well established (I associate it mainly with the Apache Software Foundation).

To me "donation", based on its ordinary usage in English, suggests "here's something I don't need anymore; you can have it, I won't have any further involvement in it." That does fit certain situations (an example that comes to mind is Oracle's transfer of OpenOffice to the ASF).