Greetings,
I have a beige G3-400 minitower with 512Mb Ram, 18Gig SCSI HD, and 2xDVD-ROM that previously has OS 9.2 on it. I then wiped it and attempted to install Debian Linux .. after some stubborn isssues with OpenFirmware and this and that!...I have post-poned this and decided to try and install OS 10.2 on it. Is this possible using the install cd that comes with a new Imac?

Possibly, but that's not legal. If you're a student or work for an educational institution, you can get a discount on the retail package. If not, full retail on it's not bad considering what you get.

10.2 will run on a beige G3 just fine, but:
1) you'll need to update the firmware on your SCSI card.
2) you'll have to create a partition completely within the first 8 Gb of the hard drive to install Jag onto.

I have it running on two G3-266 desktops (each with 512 Mb RAM and a 40 Gb drive) without issues. OS X in general is optimized for G4 processors, so it's not the fastest OS on a G3, but it's far more stable than 9, in my experience.

So, the short answer is: Yes, it'll work. Just don't be cheap about it and buy a retail pack. You also get some support from Apple that way.

It won't work, but it would be perfectly legal as long as the new iMac isn't running the same copy of OS X.

p