The font atract-rom.ttf is made from the character sets of AltirraOS-XL-XE.rom, at $E000 and $CC00.

AltirraOS-XL-XE.rom and AltirraBASIC.rom are built from Avery Lee's Altirra sources
(Altirra kernel ROM replacement and Altirra 8K BASIC), distributed under this notice,
reproduced as it appears in the source files (for example src/Kernel/source/main.xasm):

    Copyright (C) 2008-2016 Avery Lee

    Copying and distribution of this file, with or without modification,
    are permitted in any medium without royalty provided the copyright
    notice and this notice are preserved.  This file is offered as-is,
    without any warranty.

Altirra BASIC carries the same notice, Copyright (C) 2014 Avery Lee.
Source: https://www.virtualdub.org/altirra.html
The Altirra emulator itself is GPLv2; these ROM images are not part of it.
ATRACT serves these two files to run programs in the visitor's browser and keeps
this notice beside them (ADR-002: the licence notice travels with every copy).