I'm a small-time open-access publisher, not a lawyer, but have done lots of research about this, and spoken to Creative Commons counsel about it. So I will make a proposal.
@Neo wrote in the question I mentioned:
i dont think that is a copy right issue: journals are meant to be
cited, as long as they are cited. I do not need any permission to use
a diagram from a journal article in any form, if properly cited.
This is not quite right. It is a copyright issue, and you do need permission. Most journals (e.g. GSA) have clearly stated terms of use, and often say something like "You can use one figure or short excerpts without permission." Others are rather strict (e.g. AGU) and storage and digital reproduction are excluded entirely. You absolutely do need written permission for any use beyond the publisher's terms. Often this is handled through the CCC (usually for a fee, sometimes quite large).
At least in some jurisdictions, we can make a fair use argument. This is a matter of judgment and I agree that SE probably qualifies in most cases, provided the excerpts are small and properly cited and labeled (see below).
There is also the issue of Stack Exchange's open license, CC-BY-SA, which can in principle contain unlicensed material but probably shouldn't. Wikipedia, which uses the same license, has zero tolerance for it. There are exceptions, like a fair use claim for using a low-res cover image as a visual representation of a book, but even these are challenged all the time.
If a person really has to use unlicensed material, they should do three things:
- Ensure that the use complies with the rights holder's terms.
- Follow the advice of Creative Commons and state explicitly that it is copyright and not licensed, name the rights holder, mention or link to any explicit or implicit permission they have for re-use (e.g. in the terms of use), and link to the source.
- Cite the source with a full bibliographic citation and, preferably, a DOI.
Notwithstanding all this, here's why I think we should strongly discourage the use of unlicensed copyrighted material:
- It would encourage the creation of more open access material, for example to illustrate a point.
- It would increase the impact of open work, like Wikimedia Commons, Figshare, PLOS ONE, and so on.
- It would reduce the impact of non-open work.
I realize this probably all seems pedantic to most people, but I think most of us would agree that open access to scientific knowledge is important for society, and copyright abuse is rife in our field (just go to a conference and watch the parade of unlicensed material in people's talks). Instead of ignoring the issue, we can play a part in growing the amount of open material in geoscience.