There are a few targets (clearfog, turris_omnia) and features (signing in mkimage) in the Debian build of u-boot that have been avoided due to lack of clarity on Licensing issues regarding GPL and OpenSSL compatibility issues.
A reasonable description of the issue GPL linking against OpenSSL issue:
https://people.gnome.org/~markmc/openssl-and-the-gpl.html
It seems like Licenses/Exceptions might be attempting to address this issue, but it is not absolutely clear that this applies to linking against OpenSSL:
GPL License Exception:
Even though U-Boot in general is covered by the GPL-2.0/GPL-2.0+, this does *not* cover the so-called "standalone" applications that use U-Boot services by means of the jump table provided by U-Boot exactly for this purpose - this is merely considered normal use of U-Boot, and does *not* fall under the heading of "derived work".
The header files "include/image.h" and "arch/*/include/asm/u-boot.h" define interfaces to U-Boot. Including these (unmodified) header files in another file is considered normal use of U-Boot, and does *not* fall under the heading of "derived work". -- Wolfgang Denk
Some recommended text to apply an explicit exemption for GPL+OpenSSL:
https://lists.debian.org/debian-legal/2004/05/msg00595.html https://doc.qt.io/qt-5/qtnetwork-index.html#licenses-and-attributions
Some example text taken from https://sources.debian.net/src/offlineimap/7.1.2%2Bdfsg1-1/COPYING/#L353
In addition, as a special exception, the copyright holders give permission to link the code of portions of this program with the OpenSSL library under certain conditions as described in each individual source file, and distribute linked combinations including the two. . You must obey the GNU General Public License in all respects for all of the code used other than OpenSSL. If you modify file(s) with this exception, you may extend this exception to your version of the file(s), but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version. If you delete this exception statement from all source files in the program, then also delete it here.
If most explicit clarification could be made on this issue, ideally through commits to u-boot git, I would be able to enable more features in the u-boot packages in Debian!
Thanks!
live well, vagrant