Cyclone IV with PCIe transceiver and Linux GPL license

The answer to this is yes if you add a kernel module you need to release your code. Embedded FPGA SoC developers using Linux beware (as well as PCI express FPGA Linux developers).

Here is a good guide for how to comply.

https://www.softwarefreedom.org/resources/2008/compliance-guide.html

This applies to ANY flavor of Linux. The GPL license for the Kernel stays the same no matter what.

One way around this is to use a binary blob (as many Android device developers do).

https://en.wikipedia.org/wiki/Binary_blob

However a kernel module built against a compiled kernel will always be under the GPL (i.e. you have to open source your code for that kernel module).