A few more quotes from that gnu.org website
"In an object-oriented language such as Java, if I use a class that is GPLed without modifying, and subclass it, in what way does the GPL affect the larger program?
Subclassing is creating a derivative work. Therefore, the terms of the GPL affect the whole program where you create a subclass of a GPLed class."
and (the interesting part of this Q&A are the Bison provisions)
"Can I use GPL-covered editors such as GNU Emacs to develop nonfree programs? Can I use GPL-covered tools such as GCC to compile them?
Yes, because the copyright on the editors and tools does not cover the code you write. Using them does not place any restrictions, legally, on the license you use for your code.
Some programs copy parts of themselves into the output for technical reasons—for example, Bison copies a standard parser program into its output file. In such cases, the copied text in the output is covered by the same license that covers it in the source code. Meanwhile, the part of the output which is derived from the program’s input inherits the copyright status of the input.
As it happens, Bison can also be used to develop nonfree programs. This is because we decided to explicitly permit the use of the Bison standard parser program in Bison output files without restriction. We made the decision because there were other tools comparable to Bison which already permitted use for nonfree programs."
more info on this can be found at: GNU General Public License v2.0 w/Bison exception | Software Package Data Exchange (SPDX)
" Bison Exception
As a special exception, you may create a larger work that contains part or all of the Bison parser skeleton and distribute that work under terms of your choice, so long as that work isn’t itself a parser generator using the skeleton or a modified version thereof as a parser skeleton. Alternatively, if you modify or redistribute the parser skeleton itself, you may (at your option) remove this special exception, which will cause the skeleton and the resulting Bison output files to be licensed under the GNU General Public License without this special exception.
This special exception was added by the Free Software Foundation in version 2.2 of Bison."