First, thank you for being an honest person and finding this article. Secondly, it depends, but we’ll walk through it. The first thing you should know is that there’s a licensing guide that covers these details. As of the time of this blog post, it can be found here: http://aka.ms/tnydo0
First the basics; There are three flavors of Lync CALs; they are Standard, Enterprise, and Plus. You’ll always need a Standard CAL, it’s your basic CAL for Instant Messaging, presence and one-to-one audio/video chatting. The other two you would need in addition for the Standard CAL. Enterprise is for conferencing (this includes desktop sharing and almost any other modality with more than two users present with the exception of IM). The Plus CAL is for enterprise voice or phone use, but like the Enterprise CAL this also includes voice conferencing. Each of these CALs are broken into two types; the device CAL and the user CAL. The user CAL is of course a CAL assigned to a user. That user can use any number of devices as long as there’s a CAL purchased for them, but other unlicensed users can’t use their devices. A device CAL would be assigned to a device such as a phone, and unlicensed users can use this device but can’t use another unlicensed device.
That’s good to know, but doesn’t quite answer the question. The answer can be found in the guide linked above in section 6.1.1.
Optimized phones that are primarily used by Lync users licensed to use Lync under a user based CAL approach do not require additional CALs to connect to Lync Server. Examples would be hot desking phones that are used in a shared cubicle environment where all users are licensed for Lync or conference room phones within an environment where all or most conference room users are licensed for Lync.
Optimized phones that are primarily used by individuals not licensed to use Lync require a Lync Standard CAL and a Lync Plus CAL. Examples would be common area phones in reception areas, conference phones in meeting rooms used primarily by covered employees not licensed for Lync, and shared phones used by multiple users not licensed under Lync user CALs (but who may use Lync via shared computers covered by Device CALs).
 Lync phones do not require Windows CALs as they authenticate against Lync Server, not Active Directory and do not access Windows Server features
The guide continues in section 6.1.2 to say that compatible/qualified phones for Lync have the same licensing requirements as the optimized phones referenced above.
So, let’s look at the conference room phone example. If all of your users are licensed with Lync user CALs, they can freely use the conference room phone even if it’s logged in as a common area phone or different user account. The guide says “most conference room users are licensed for Lync” and I take it to mean that if your mother shows up in your conference room to congratulate you on your Lync rollout during a call, you don’t need to quickly buy her a user CAL.
Now let’s take the same room and put it in a school. The students aren’t licensed with user CALs in this scenario, but they’re the primary users of that phone. In this case, then you will want a Standard device CAL and Plus device CAL for the phone.
Please understand that of course I do not work for Microsoft and cannot speak for them, this is simply my interpretation of the licensing guide. License at your own risk, and thank you for reading.