It's buildroot based system.
I don't believe there's a write premission, the system is ro except the userdata partition.
The user possibly can remount the partition with write permission, the problem is that probably /usr is squashfs file mount from the system partition so I'm not sure if the user can remount the system partition without unmounting the squashfs.
But why going all this trouble ? XBMC should have the (experimental) Network Manager so the user can set the dns manually (maybe not with dhcp but true for static ip).
Anyway I didn't tried this specific image (as I don't have a Geniatech device) but I would say f*** Geniatech, they are GPL violators (where are the Linux sources ?).
Go to Corey's thread on XDA and ask to be a tester for your device, Corey already posted that he plans to add support to these devices and that he needs testers. this is the best choice for getting proper community support with full access to sources so that any developer can fix issues and build update images.