Not necessarily caused by Odyssey, though.
Try to use an iPad 2 with 512MB of memory to browse the internet these days. Not a pleasant experience. Frequent browser crashes due to insufficient memory, etc.
Yes, it's just how modern browsers are. OWB isn't cutting edge but it's modern enough to need bucketloads of RAM. Disproportionately more than anything else on MorphOS.
When you've only got 2 GB of address space and no virtual ram to swap it and back and make the physical memory contiguous again, the problem of heavy memory usage tends to be even more acute.