Out of curiosity, I took a look at the list of "adopters" (licensees) and the RPi foundation is listed.
https://www.hdmi.org/learningcenter/adopters_founders.aspx#R
That definitely suggests that development boards are also subject to licensing.
Sure. Why would "dev boards" be exempt, when they are products offered for sale to third parties?
Just because dev boards are usually not considered end-products per se. Of course this is often borderline.
The problem here is we have to distinguish the licensing from the royalties. Whereas, if we understand it well, only the final product would incur royalties (which obviously would be hard to enforce for dev boards: what happens in case the dev board is included in some end-product? Wouldn't it become just a component of it? And thus having paid royalties on the dev board would imply paying royalties twice actually for the same end-product? Doesnt seem right.) - becoming a licensee in itself (without considering any royalties on individual products) is probably mandatory just for IP reasons. So I'm guessing here that even a component manufacturer has to become a licensee (at least to be able to use the HDMI specs and the HDMI name), even though it doesn't have to pay royalties on the sold components themselves (as they are just components). Does that sound right?
I may have gone a bit far considering the RPi as a dev board though, as the RPi foundation classifies it as a "computer" and not as a development tool.
https://www.raspberrypi.org/documentation/faqs/#introductionGenerally speaking, the so-called "SBCs" are borderline between dev boards and end-products.
As an example, let's take a look at the BeagleBone Black. It has HDMI, can run Linux, and in many aspects is not unlike an "SBC" like the RPi.
In its documentation, it's clearly stated:
BeagleBone Black is not a complete product. It is intended solely for use for preliminary
feasibility evaluation in laboratory/development environments by technically qualified
electronics experts who are familiar with the dangers and application risks associated with
handling electrical mechanical components, systems and subsystems. It should not be
used as all or part of a finished end product.
So are royalties to be paid on that? I wouldn't think so. But I may be wrong.
Would the developers have to be HDMI adopters? It's still very unclear to me, as they would just use off-the-shelf components for which other licensees have already been licensed for.
The devil is always in the details.