That's the version of simplejson that comes with ubuntu feisty, and the one that we've required for most of our history. Currently the Ubuntu dapper buildslave fails (see issue #534), and setting the simplejson requirement to be >= 2.0 would fix that failure, but I don't understand why.
# We had a unicode problem with simplejson 1.8.1 on dapper -- see ticket #543,
# but we want to install using Gutsy or Hardy simplejson .deb's if possible --
- # see ticket #555.
- "simplejson >= 1.7.1",
+ # see ticket #555. Feisty has simplejson 1.4
+ "simplejson >= 1.4",
"zope.interface",
"Twisted >= 2.4.0",