According to the FAQ at patchburn.de:
Q: Will PatchBurn help me to use CD/DVD writers with iDVD?
A: Yes, with some restrictions: You need to have a G4 processor or newer. iDVD will not run on a G3 processor or older. Furtheron you need to have at least Mac-OS X 10.3.6 and iDVD 4.0. iDVD is not officially supported by PatchBurn 3, but it may work, if you are using an internal DVD-writer connected to the IDE-port. If you are using an external DVD-writer via Firewire, activate the button "Install support for iDVD 4" in the "Experts Mode". PatchBurn 3 then installs two resource files called "Hurz" and "Pfurz" in your home directory. If these files are present, iDVD shows an hidden dialog box to burn to an external DVD-writer or to write a disc image onto the harddrive. To get this hidden dialog in iDVD press and hold the control-key while clicking two times at the "burn DVD" symbol (lower right corner of the iDVD window). Caution! This is a hack! Apple may remove this feature in future versions of iDVD. It should work so far in iDVD 4.0 and 4.0.1.
So you _might_ be successful. Seems to depend on a couple of things.
Another entry in the FAQ could be helpful, too:
Q: iDVD 4 recognizes the drive but will not complete a DVD. I installed Patch Burn and was able to ctrl-click and select my drive in iDVD. The burning process made it to Stage 4 but then it stayed there all night long and never finished. What did I do wrong?
A: Save the DVD as an image file and burn it later using Disc Utility. In most cases this will work around the problem.