Most commercial add-ons out there use the standard marketplace licence provided by the concrete5 marketplace:
http://www.concrete5.org/help/legal/commercial_add-on_license/...

There you can read the following:
" 1. License Grant. Subject to the provisions of this Agreement, Customer is granted a limited, non-transferable, non-exclusive license to use the Software Application for a single website and a single staging or development version"

And the part you're interested is:
"...to use the Software Application for a single website and a single staging or development version"

So, this basically means that you can have the add-on installed on the site in its different versions (development and production environment = website).

Also, if you move your site to another domain, it is 100% ok.

Actually this licence term would limit the usage to the following cases if interpreted 100% accurately:
- Development & Production
OR
- Staging & Production


So if you follow this licence term 100% accurately, these (for example) ARE NOT possible (as it states):
- Development & Staging
- Development & Testing & Staging & Production


However, I think it's just a thing in the licence terms that's not 100% thought out. Franz (c5 CEO, frz) has personally said that it's totally ok to have the add-on installed on different versions of the same site, as long as it's only installed to ONE instance of a publicly available website that is used for real.

And using it for real means that IMO you can also have a publicly available staging environment with the same licence, although the licence terms do not allow that 100%.


Legal things, not so easy always, especially when dealing with lawyers from the US... :)


Br,
Antti / Mainio