clock...
You are unfortunately, incorrect.....
The Mac App Store terms and conditions allow you to install an App bought via the App Store on as many Macs as you own or control, for private use, using your Apple ID and the Purchases tab in the Mac App Store Application.
Commerical use has somewhat different terms....
http://www.apple.com/legal/internet-services/itunes/appstore/jm/terms.html
MAC APP STORE PRODUCT USAGE RULES
ℹ If you are an individual acting in your personal capacity, you may download and use an application from the Mac App Store (“Mac App Store Product”) for personal, non-commercial use on any Apple-branded products running Mac OS X (“Mac Computer”) that you own or control.
(ii) If you are a commercial enterprise or educational institution, you may download a Mac App Store Product for use by either (a) a single individual on each of the Mac Computer(s) used by that individual that you own or control, or (b) multiple individuals on a single shared Mac Computer that you own or control. For example, a single employee may use a Mac App Store Product on both the employee’s desktop Mac Computer and laptop Mac Computer, or multiple students may serially use the Mac App Store Product on a single Mac Computer located at a resource center or library. For the sake of clarity, each Mac Computer used serially by multiple users requires a separate license.
I have certain apps downloaded and installed on 7 different Macs here... without issue.
You are probably thinking about authorizing up to 5 Macs per Apple ID for eligible content (Music/Movies etc) in iTunes.... which is a different matter entirely... and even that changed recent to 10 devices with no more than 5 devices being authorized via iTunes... presumably to take into account the number of Mac owners who also own multple iOS devices as well as multiple Macs these days...
ℹ You may auto-download Eligible Content or download previously-purchased Eligible Content from an Account on up to 10 Associated Devices, provided no more than 5 are iTunes-authorized computers.
Cheers..
Nigel