The short answer is yes, if you are using your G5 as a print server it will continue to work.
... my Powerbook running OS 10.6.8.
Please clear up my confusion about this though - a Powerbook can't run Snow Leopard. Did you mean a MacBook?
If your G5's only task is to act as a print server - in other words, your LaserWriter must be connected directly to the G5 for it to print - you can relieve it from that duty easily enough.
This USB to parallel adapter cable will work, I have tried it myself with your printer:
http://www.amazon.com/IOGEAR-GUC1284B-USB-Parallel-Adapter/dp/B00018RT1E/
Plug it in and it works. Read this old thread for more: USB to Parallel Cable for LW Select 360?
Since you would like to print from a portable, a wireless print server is an ideal solution. These are becoming hard to find with a parallel port, but this one should work:
http://www.trendnet.com/products/proddetail.asp?prod=100_TEW-P1PG&cat=46
I have a similar one, tried it with your LaserWriter and it works too.
These solutions mean you will also be able to retire your AsanteTalk bridge.
Here is another old thread good for some more details:
Laserwriter Pro 630, Mountain Lion, and Macbook Pro
The only disadvantages I have been able to determine while either the USB to parallel adapter cable, or the print server, is that high level bidirectional communication does not work. The manifestation of this is that the printer will not be able to tell the computer that it is out of paper or that it has a paper jam, for instance. However, the print server and cable are both intelligent enough to know when the printer is ready to accept the job, or not. In other words, basic printing functions will be fine, but the printer will lose its ability to communicate things like a page count, or that its toner is getting low.