Will Robertson wrote:
> 
> Also, is it redundant to have checks for eTeX since we're requiring it,
> anyway?
> I'm also guessing we can drop the aleph conditional these days?

The current expl3 bundle doesn't actually complain if one does

\let\eTeXversion\undefined

before loading expl3. So the test is still valid until that changes:

\documentclass{article}
\let\eTeXversion\undefined % Or use plain TeX, of course
\usepackage{expl3}
\begin{document}
\csname engine_if_etex:F\endcsname {NO ETEX!!!}
\end{document}
-- 
Joseph Wright