You've probably noticed by now, that there's a wildly confusing variety of this kind of software available, much of it open source and much of it with a similar-sounding name, like "LogicSim", "Logisim" (without the c), "Logic Simulator", "Digital logic simulator" and so on. To make things more confusing, such projects are extremely easy to start, easy to fork, and unfortunately also easy to abandon.
The following is an attempt to provide an overview of some of the more popular variations and forks, based in part on a "survey of simple logic simulators" by hackaday.
We'll start with "LogicSim", for obvious reasons. There are a few here:
This has probably the largest number of independent forks, ports and reinterpretations.
A restart from the same author as the original (abandoned) Logisim, ✗ abandoned in 2014.