Edit: though I thought about it a little more. The more interesting question is regarding the standard library, rather than the compiler. Applying different licenses to the two is not unusual (gcc is GPL, glibc is LGPL). From what I can see, the standard library is embedded entirely into the compiler, and thus yeah, I do think programs that use this would actually have to be GPL. Not that that's a bad thing though :)
More important than the standard library (which isn‘t so standard, just conventional, see musl) is the GCC Runtime Library, which is GPLv3, but with the "GCC Runtime Library Exception".
There is also an interesting question about license compatibility between GPLv3 and GPLv3 with RLE, but that is mostly ignored by everybody.
Unless KamilaLisp specifies exceptions to the GPL, it means that if you ship your own KamilaLisp program in a way that is combined with KamilaLisp (for instance compiled into one big executable that includes the KamilaLisp run-time) then the entire combination has to be distributed under the GPL, meaning that your program has have a GPL-compatible open source license.
Programs that are not combined with KamilaLisp, only requiring an installation of KamilaLisp for their execution, almost certainly don't have to be GPLed.
Edit: though I thought about it a little more. The more interesting question is regarding the standard library, rather than the compiler. Applying different licenses to the two is not unusual (gcc is GPL, glibc is LGPL). From what I can see, the standard library is embedded entirely into the compiler, and thus yeah, I do think programs that use this would actually have to be GPL. Not that that's a bad thing though :)