I don't buy it. I think it's OK to rescue orphaned projects and place them on something central like riscos.info, and it's OK for riscos.info to mirror a project if the source/binary licensing allows. But in the case of ArcEm, the source wasn't lost or orphaned - it was readily available from sf.net; there's little reason to close that down - unless the project as a group consented to it. Mirror or link to it, sure.
it's not quite the same, but, as a similar example, I couldn't imagine TIB copying the contents of the drobe.co.uk sub-domains onto its own server and then urging drobe users to remove said content from drobe.co.uk.