Can I use a Unity mixer to act as an OR logic module for gates? Will I fry modules if I have too many gate signals going at the same time? Alternatively, are there any highly dense OR logic modules available (Intillijel made one, but I think they don't anymore)?

No, no, Intellijel still makes their OR logic module, it just takes ordering directly from Intellijel's site. I'm still curious if a unity mixer would work however.

No. Diode or Boolean ORs are actually rather different from a basic mixer. With an OR gate (of either type) the module reads the incoming gate signals and combines AND regenerates a resulting +5V gate. In a diode OR, this regeneration doesn't happen, but the functionality is still the same: combine gates to get a "composite" gate. This is different from a unity-gain mixer, where incoming signals are simply mixed together...this won't arrive at that "composite" gate result.

Another module this all gets confused with would be adders. In their case, you input various CVs, and the output is the arithmetical sum of the incoming voltages. These won't work to combine gates AT ALL...what you'll actually get when two gates coincide are the +5V amounts when the gates aren't coincidental, and +10V when they are. However, you CAN still arrive at a single gate by feeding the adder to a comparator and setting its threshold to, say, +6V so that whenever that level is exceeded, the comparator will fire off a gate. But it won't be a true "composite" gate; rather, this patch would only fire a gate off during those coincidental points...which can ALSO be useful, but it's not what an OR does.

I suspected as much. I would be concerned with feeding too high a voltage to some other module after mixing two or three +5V gates into one +10V 0r even +15V signal.

I've used a Quadratt as a cheap and dirty "AND". As long as the module you're feeding has a minimum voltage to trigger that input, you can feed two gates into the Quadratt and attenuate them so that each individual gate is under the threshold. But when both are present, you're over the threshold.

A little off topic but still relevant IMHO. But should work with any DC compatible mixer with attenuation.

Ronin: Yep. And that just shows that if you're not set up for method #1, there's almost certainly a "method #2" hiding in the rig somewhere! Just requires ingenuity and necessity...