OK guys, I spent some time fixing up the 68k toolchain for NetSurf, so it now builds again and all the dependent libraries build too.
I've also spent quite a while fixing all the compiler and linker errors for the OS4 build, when passed through the 68k toolchain. It now builds and runs (don't get too excited) as far as errorneously displaying the splash window as a long thin window at the top of the screen. It then crashes, probably somewhere between initialising the DataTypes handler and initialising NetSurf. If I run it on OS4 (yes, that earlier test was on OS3.5, just to check I got the same thing) I can ignore past the crash, and then it crashes creating the main window.
I should probably try to build a simple ReAction example to check that side of things is working, as the splash window couldn't be much simpler so it makes me think the macros are somehow screwed up.
I'll probably keep poking it with my stick but it would progress a lot quicker if I had some help. Anybody?