the latest hso driver 1.12 is for 2.6 kernels,and only version 0.1 was for 2.4
here's source and compiled hso.o against 2.4.37.2 kernel for 1.9.2.7-d firmware (yes, you have to flash it to get driver working)
Code:
[admin@router /home]$ uname -a
Linux router 2.4.37.2 #2 2009-07-28 12:34:25 YEKST mips GNU/Linux
[admin@router /home]$ insmod /home/hso.o
[admin@router /home]$ lsmod
Tainted: P
hso 31816 0 (unused)
usb-storage 62968 1
sd_mod 12660 2
scsi_mod 72624 2 [usb-storage sd_mod]
ehci-hcd 28196 0 (unused)
usb-uhci 27380 0 (unused)
usbcore 78456 1 [hso usb-storage ehci-hcd usb-uhci]
but i have no modem of this kind, so can't test if it's working driver.