This problem also appears for builds on Sparc64. It seems to come from a problem with the architecture specific system-call tables.
There is a workaround available:
go to your /usr/src/linux or whereever you have your linux-headers installed, then open scripts/mod/modpost.c and do a search for "GPL-incompatible" you will find two lines around line nr 1100 which says fatal('GPL-incompatible.....') - go on an change the word fatal to warn. Then save and close the file. Still standing in /usr/src/linux now run "make scripts" to recompile the modpost script.
This workaround enables the module to be loaded, at least for sparc64. Futhermore it does actually seem to work, i have seen no problems so far with 1.4.5 in ubntu 8.10 installed with this workaround.