Feel free to offer corrections, but I believe the original iBook doesn't suffer from the 8GB limit, despite it being so mentioned in Apple's KB article.
I picked up an original 300/32/3 ugly clamshell recently having always wanted one.
Digging through parts I had laying around I put a 40gb 7200 rpm drive in. Using a modified Tiger install disk (bypasses hardware check, no need for Xpost facto) I booted and started installing, then remembered the 8gb limit.
I created three partitions, 8gb, and two more. The last 15gb one I installed tiger into, and it booted! It was entirely outside of the first 8gb. It also didn't complain about an unsupported partition.
I then wiped the partition and installed OS 9.2 instead, again in a partition that is 15 gb in size on the end of the drive. It booted and worked faultlessly.
So I've come to the conclusion that the original iBook doesn't have this limit.
Note the drive was partitioned using Tiger's disk utility, which may have some bearing, and also was running the last firmware update Apple made.
I've experienced the 8GB limit before on original iMac and beige G3, so I know the symptoms, but this iBook seems immune.