Indeed, as a kid of 10, I remember learning C/C++ thanks to DJGPP, a DOS port of GCC, being free software. I didn't have any money to buy a commercial compiler, though I never asked my parents. I wasn't sure how to frame the question, I guess. Well, regardless, getting your hands on a commercial compiler wasn't that difficult in the late 90s/early 00s. Soon after though small non-commercial indie games kinda died out and everyone was using DirectX using MSVC on Windows, until SDL came out.
SDL appeared in late 90s / early 00s, that's pretty much when it became popular (e.g. most early Loki Linux game ports from used SDL).
As far as compilers, Borland shipped a free version of their C++ Builder 5.5 compiler right around that time, too, so on Windows we had that in addition to MinGW.
Many HN readers frequently forget they lived in the perfect storm to allow their skills to grow.