I have ported the Arduino core library to NIOS soft-core CPU. This core comes with a "Hardware abstraction library", which is freely available (e.g by downloading the FPGA development environment) but AFAIK is not GPL. My library includes modified Arduino files, but not the HAL files.
Am I right to assume that I can redistribute my work under the same license as Arduino (GPLv2)? Does HAL fall under the definition of "System library" in GPL terms, or do I have to distribute it? I would really prefer not to, because HAL is by definition hardware-dependent, so my version would be useless to anyone using a different hardware configuration, and the whole point of FPGAs is the ability to experiment with hardware.