I've just installed the Open-Audit community edition and it requires an upgrade to the "professional free" to discover up to 20 devices. I was not able to run any discover from the community edition and even the tutorial was recommending to install this "professional free".
On the other hand I was told that the community edition does not have limitations, hence installing Professional Free will just create an unneeded limitation.
Can you please clarify?
Please upgrade your install to v2.2.5; the version you currently have installed, v2.2.4 has known issues with discovery and scheduling which were fixed in the latest release.
You are not required to active the free 20-device license for Open-AudIT Professional, it is a courtesy so you can see the differences between the Professional/Enterprise commercial versions and the free Community edition.
When you see the pop-up just scroll down and click the button that says Do Not Show This Again.