According to the EULA the license would allow for one Production and two non-Production environments. Below is a link where you'd want to select the EULA option if you'd like to review it:
Though as a bit of a time saver I do see the following snippet in section 3.3.1 for Non-Production environments
You may use the Server Software in a technical environment and on the platforms and configurations specified in the Documentation, solely for internal
development and testing in connection with your licensed Software,or for disaster recovery purposes (“Non-Production Environment”). Your installation, activation or use
of a copy of the Software in a Non-Production Environment is limited to the same number of Authorized Users and/or permitted number of Cores and/or computers
as provided under Section 3.1 above
If you have interactor license (sounds like you do), there's no limitation on how many environments you can install. If you have server core license, 1 production and 2 non-prod environments per Mark's post above.
You really should confirm with your sales rep.
With the given info provided, yes you could use 5 user licenses on one machine and the other 5 on a different machine. Again, please speak to your sales representative to confirm.
Hey John! Long time. Hope you're doing well.
FYI, what you've written here is not correct. Even with an Interactor license, you can only install to a single prod environment and two non-prods. See section 3.3.2 of the EULA which makes no distinction between a core & interactor based system in terms of how many environments you can run.