I too have been developing open source Twitter applications. I'm using
Perl though, not PHP. I am about to release all of my code that
operates *unauthenticated* in open source form, but I am strongly
leaning now towards *not* providing open source solutions for
authenticated access to the Twitter API.
The risks are too great and the rewards are too small. Perhaps when
the oAuth-authenticated API is *delivering* the 1500 calls per hour
promised, the rewards will change, but right now, for things like
tweet and user data acquisition, there's not enough difference between
the unauthenticated 150 and the oAuth 350 calls per hour to justify
the extra code.
M. Edward (Ed) Borasky
"A mathematician is a device for turning coffee into theorems." - Paul Erdos