I thought about the same some time ago and found the only issue would be bundeled Software that is still being licensed (e.g. 3Deep Colorific)
I contacted the current company a long time ago concerning exactly this issue but never got a response.
So for as long as there is no such Software on it, I consider the contents of Driver Discs as freeware.
(technically, many - if not all - 3dfx drivers clearly state that all content is subject to 3dfx licensing, but not even after modifying the code the current license holder (NVidia) ever raised their voice... Therefor I'd say all Drivers, Demos, Patches etc. are after all this time unlicensed / abandonware)
For the few remaining risks I pay lawyers since ages, in case I'd need them I'd at least get them working for my money
As any contained Software is technically obsolete by all standards today, my position is that these CD's do not pose any risk for redistribution - for as long as it's free of commerce.