Hulu is VERY different from YouTube. Hulu is a joint venture of NBC Universal and News Corp. The shows you can view there are owned by folks running the site. YouTube, on the other hand, relies on user-uploaded content, and is rife with copyright violations (hence the Viacom lawsuit).
AbraTube, however, as far as I can tell, is not doing anything illegal. Any videos there are linked from YouTube (which the folks at YouTube have no problem with
), so any copyright issues would fall into YouTube's lap.
However, I am not a lawyer, so my interpretation of the law may not be 100% correct.