I know that editing GPL source code is considered as a "modification", which means all the copyleft rules apply.
However, most software includes configuration files and makefiles which you can tweak before rebuilding. Does that count as modification?
For example, I am using the
swupdate package through Yocto. I override the
meta-swupdate layer to specify specific configurations (e.g.
CONFIG_LUA_PARSER=y to enable LUA parser), and then build swupdate.