Yes, I'm the porter of it.
The main reason it's slow is that it uses chunky graphics rather than planar graphics, it also does a lot of floating point calculations. And as noted it is written in C.
It could perhaps be rewritten to use bobs etc. which might speed it up somewhat.
It runs playably for me under WinUAE. 8-bitplane AGA screens are not fast, RTG should give acceptable performance. You must remember that at any given moment it is calculating the physics of, and handling the collision and display of up to 3000 or so distinct objects.
Any poor coding should be blamed on the original author, I just did a fairly minimalist port, I haven't done anything which would make it any slower :-)
If anyone wants to speed it up, code submissions are welcomed.