I'm thinking of buying Mach4 Hobby, but I currently use Mach3 on 3 machines (1 cnc router, 1 Sherline mill and 1 Sherline lathe.)

I've read conflicting information about how many PC's a single copy of Mach4 can be used on.  Some of the confusion may come from changes in the way licensing has been handled, but the Newfangled website currently says "IMPORTANT NOTE: The LICENSE will only work for the Computer for which you supply the PC ID at checkout. Each PC has a unique ID code and the license works in coordination with this code."

Can someone explain if a single purchased copy of Mach4 Hobby can be used on my 3 PC's?

The license server allows you to generate license files for yourself by supplying a PCID
code for each machine that is to be licensed.

The license server will enforce a limit of 5 active license files for your purchase of one
license.

License files for computers no longer in use can be de-activated, but the server does
monitor the turnover rate and may require you to contact support if it is excessive.

If you plan to use your machines commercially for production work, you are expected
to purchase one license per machine.

In summary, a hobby user could as an example, run 3 real machines, have a desktop to
test screens and scripts, and a laptop for convenience.

That's a great explanation and perfect for me.  Time to pull out the plastic!

Thanks!