The licenses of logotypes are different animals from licenses of source code and of tool icons used in open source applications. At least some open sourced applications and projects have logotype licenses that are not licensed under a free (libre) license.
License of light bulb logotype for FreeMind
The light bulb logotype provided by Frank Appel has the following license.
- All the images are copyright (C) 2005 by Frank Appel (Foundax.com). The right is granted to distribute the icons and the splash screen as part of free mind mapping software FreeMind, either in their original form, or converted to other image format than the original PNG.
See the patch with the light bulb logotype.
Licenses of open source projects
Debian and FreeBDS are examples of open source projects that have non-open source license for their logotypes. It follows from the following links.
Licenses of GNU and FSF logotypes
Free Software Foundation seems to have no explicit licenses of their logotypes. This conclusion follows from the following links.