Yes, when you purchase one subscription of Microsoft Office 365, you receive the right to install 5,5,5 copies of Office on different devices for that single user. We have highlighted the following points that speak to this licensing fact:
From Microsoft Official Volume Licensing Documentation*:
Italics are ours for clarification or emphasis:
In our words:
Each user of Office subscription, E3, or E4 can run up to 15 copies of Office - up to 5 that are full function 2013 (PC or Mac) AND up to five on mobile phone AND up to five more copies on tablets (currently only iPad Office is available – Android tablet to follow at a time that is unclear). Additionally, any user who has access to the web applications (K1, E1, E3, E4 plans or a-la-carte) could access Office functionality via any modern web browser.
Need a quick comparison chart? https://www.interlink.com/component/easyblog/?view=entry&id=26
*To check out the details, please see the Microsoft Office Services Use Rights Document and lookup Office 365 ProPlus: