User blog comment:Carbonite 0/MW3 Real Life Achievements/@comment-2045634-20120212211745/@comment-3123696-20120212220842

Yes, Source is a 2004 engine. And DOTA 2 is also on Source engine. Altought they always update to more modern versions. For example, when comparing 2004 Source with 2011 source, there's a much bigger difference with graphics.