In addition to well-known truths about this configuration, I will add a few more considerations. They are accumulated through the years when I was thinking how to reveal the truth to my students so that they not only know what it is but understand why it is made so...
Output quantity. Actually, the output quantity of an open collector stage is resistance; it does not produce voltage or current. So, its output is passive, "dead"... and this device cannot supply a load... it needs an additional voltage source (the same or else's power supply in series to the load). In logic gates, this "resistance" is zero or infinite and the transistor is considered as a switch.
Logic function. The wired OR implements logic OR if we consider the input "0" as an active signal (TRUE). Actually, if we consider the input "1" as an active signal, this will be AND "gate" since the output will be high if both inputs are high. This trick is based on the De Morgan's laws and is used in diode logic gates where the AND logic gate is actually an OR gate.
Input flexibility. A great advantage of the wired OR "gate" is its flexibility - you can easily expand the number of inputs... and even vary it during the circuit operation without need of doing something more. A typical example of this configuration is the way interrupting sources are connected to the microcontroller IRQ input.
Perfect simplicity. I have put "gate" in quotes because it is actually just a node, point... i.e., nothing. Similarly, a "wired AND" is just a wire that we can cut at as many places as we want to include input "sources" (resistances, switches)... but this is not so convenient as the OR node. So, the OR "gate" consists of grounded switches (resistances) in parallel while the AND "gate" - of floating switches (resistances) in series.
The "problem" of the complementary output is that it can directly supply both ground and Vcc to the load which does not allow outputs to be joined. But still there are two situations when this connection does not lead to a conflict (short connection) between the outputs with opposite voltages:
1. Identical output signals. Although rare, it is possible to change the output signals in the same way, for example in order to increase the output current. Then the outputs help each other instead of "fighting".
2. "Forced" switching. Although it sounds unbelievable, it is possible for the outputs of two complementary stages to be connected even when they have different output voltages if two requirements are met:
- the control output is more powerful than the controlled one
- the controlled stage immediately changes its output voltage so it becomes equal to the control output voltage.
An example of such a "brutal" control is the write operation in an SPAM cell. You can see more about this trick in my RG question.
Complementary stage as open output
It is interesting to explain the role of OR-ing diodes connected in series to the complementary outputs with the purpose to make them "open outputs".
From another viewpoint, the "problem" of the complementary stage is that its output is bilateral: when the output voltage is high ("1"), it sources current to the load (if connected to ground); when the output voltage is low ("0), the output sinks current from the load (if connected to Vcc).
OR-ing diodes make the bilateral outputs unilateral. If the diode cathodes are connected to the outputs, they only sink a current from the load; if the diode anodes are connected to the outputs, they only source a current to the load.
You can see more about this explanation in my RG question.