Strict Open Hardware terms are impossible for most FPGA boards - bitstreams "languages" are closed by chip manufacturers.
Graphic chips drivers for linux require closed blobs from chip manufacturers like NVidia. Anything with linux/android and fast screen is not true Open Source. Google for "PowerVR SGX Source Code" and see that 90% of computational power of linux (GPU > CPU) is closed. Example: Beaglebone based on TI Sitara has PowerVR GPU. The most entertaining part of linux (3D gaming capabilities) is closed.
If Open Hardware product contains USB, then most likely there is black boxed microcode being injected from PC driver into board every time it is connected. FTDI is an example. I do not expect that FTDI and other USB chip makers have anything to do with Open Hardware, I only pointing at any Open Hardware projects with USB.
Intel Quark: everything is Opened, documented and published, including ... some ~4K bytes binary blob in the middle of ROM. Who knows what is its purpose ? Strictly speaking there is no such thing as Intel based Open Hardware / Open Source products.
I, personally, do not feel that Open Hardware terms should be that strict. There is some pragmatic limit for openness. But the problem is that users buy, say, Beaglebone or Galileo / Edison board and think that they support Open Source movement with their money, when in reality it is just another closed source products.
For same PowerVR GPU reason, nearly all Android phones have closed source blob between the App and the user every time when user sees any 3D graphics.
With the arrival of SecureBoot on most product worthy chips (basically any contemporary phone, PC or tablet chip) every designer is automatically, by design, is required to sign the firmware. This step involves chip manufacturers to use their private key to allow firmware to run. It is very good feature and serves for end users protection. But also means that all SecureBoot products are in no way Open Source.
So if someone (who is not chip manufacturer) announces some Open product based on any complex chip, then many of claims about openness of code should be interpreted as "Open APIs with Source examples", but not "Open Source Code of every programmable part, which you actually can build from scratch".
TLDR: All FPGAs, all high-end CPUs, all GPUs, most USBs are closed on bitstream level, firmware level and at drivers level. They are may be opened only as APIs.