Casey Brown, 21/01/2011 22:25:
In my experience the best way is actually to just do "[[m:PAGENAME YOU GOT IT FROM]]" in the summary and then anyone can reach the workspace/workspace history if they want to make changes or if they want to see who did what.
This is also the official general rule now thanks to http://wikimediafoundation.org/wiki/Terms_of_Use : «Where such credit is commonly given through page histories (such as Wikimedia-internal copying), it is sufficient to give attribution in the edit summary, which is recorded in the page history, when importing the text»[1]. This applies to all Wikimedia translations (e.g. from a Wikipedia to another one).
Nemo
[1] And "attribution" is previously defined as a link to the original page (by default).