Personally, I'd go for #3. CC-BY is just one small step up from PD, so I really don't see the practical harm. 
Wiki Commons is used for a lot of things. Copyfraud promotion should not be one of them.

I explicitly advise against using #3 for this collection or any other. Using #3 would imply that we a) didn't care about the public domain and b) didn't understand the idea behind CC licences. 
If we acknowledge such copyright claims, we also acknowledge the possibility of legal action in case of copyright violations (e.g. by violating the terms of the licence). 
Apart from this ideological thought, the actual legal enforceability of these copyright claims depends on your local jurisdiction.
Yet, I don't think the Wellcome Library released this collection with the intention of pursuing licence breaches.

As noted on https://commons.wikimedia.org/wiki/Commons:Village_pump#Wellcome_Images we could create something similar to https://commons.wikimedia.org/wiki/Template:Walters_Art_Museum_license
It's not like we didn't encounter this issue before.

Regards, Christoph



2014/1/21 Edward Summers <ehs@pobox.com>
oops, I forgot:

[1] http://lists.wikimedia.org/pipermail/commons-l/2014-January/007014.html

On Jan 21, 2014, at 12:12 PM, Edward Summers <ehs@pobox.com> wrote:

> On Jan 21, 2014, at 11:53 AM, Magnus Manske <magnusmanske@googlemail.com> wrote:
>> So, we have the following options:
>>
>> 1. Ignore them (pity)
>> 2. Upload them as public domain and re-iterate the National Portrait Gallery issue, and teach them that these open content wiki people are not to be trusted
>> 3. Label them CC-BY so the Wellcome Trust can get a mandatory attribution, which we would do anyway
>>
>> Personally, I'd go for #3. CC-BY is just one small step up from PD, so I really don't see the practical harm.
>
> Agreed, #3 definitely seems like the best course of action to try first.
>
> Magnus, I suspect you already saw that I emailed Wellcome’s image folks [1]. If you have any other contacts at Wellcome that could help out please let me know and I will email them directly.
>
> //Ed


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