I've just updated by Boids screensaver on Haikuware, you can grab it here - let me know what you think. A few points to note:
It only supports 32, 16 and 15 bit colour modes, and I've only tested 32 myself. This is because I'm using a BDirectWindow and haven't goten around to writing the other drawing routines yet!
When you have long trails with lots of boids you can see some rendering errors, this is because there's no depth testing or sorting going on, I did some experiments with alpha blending and found that reading back from the buffer killed performance, must research some kind of double buffering
The obligatory screenshot
Maybe at some point I'll add alternative colours and more, who knows?