No, 2/3 of the way down it says
This circuit requires a dual power supply to function correctly (it requires 5V, 0V, and at least -5V on the negative rail).
It’s certainly possible to build modules that run on ±5 V, or 5 V and ground, or ±12 V, or ±15 V, or, well, just about anything I guess. But combining different voltage requirement modules into the same system is complicated. There’s also questions of signal level — some modules create and expect audio signals of 5 V peak to peak (i.e. ±2.5 V), some 10 Vpp, and so on; some create and expect control voltages and gates of different levels. That can get complicated as well.
There’s a somewhat ad hoc Kosmo Specification that specifies these things and others for Kosmo modules, but non Kosmo modules from MIAW or All About Circuits or elsewhere may have different requirements.
AFAIK (I don’t follow that channel myself) the MIAW modules do work on ±12 V and can be used with Kosmo modules. Look at the schematic for one: Dropbox - Schematic_Buffured-Multiple-3x1-2.pdf - Simplify your life. At the upper left it shows the power rails marked +12 V and -12 V.
Same is true for modules from Music From Outer Space. Most Eurorack modules too, but there are a very few that also expect a +5 V rail from the power supply (the FC Power supplies have ±12 V and +5 V, but on mine I left off the +5 V part because it’s not needed for any Kosmo modules). Those one might be able to adapt by adding a +5 V regulator to the module. Modules from https://www.schmitzbits.de/index.html and http://yusynth.net/index_en.php are designed for ±15 V but many can be used unchanged or with a few minor changes for ±12 V, usually they tell you that. And so on: Lots of design sources, some directly usable in a Kosmo system, some requiring more or fewer modifications and complications.