[dsfuoi]

The 'style' even leaked out to file naming: a.c, ab.c, af.c, am.c, c.c, ca.c, cc.c, cd.c, cf.c, ...

Brilliant!

I doubt that this is either serious (unobfuscated) or handwritten code though.

[GregBuchholz]

No, it really is the hand-written source code for the J language (http://jsoftware.com/) interpreter. You may also enjoy:

https://news.ycombinator.com/item?id=2336749

http://code.jsoftware.com/wiki/Essays/Incunabulum

[kps]

For the record: http://www.tuhs.org/cgi-bin/utree.pl?file=V2/c/nc0