Licensing
LaTeX is typically distributed along with plain TeX. It is distributed under a free software license, the LaTeX Project Public License (LPPL). The LPPL is not compatible with the GNU General Public License, as it requires that modified files must be clearly differentiable from their originals (usually by changing the filename); this was done to ensure that files that depend on other files will produce the expected behavior and avoid dependency hell. The LPPL is DFSG compliant as of version 1.3. As free software, LaTeX is available on most operating systems including UNIX (Solaris, HP-UX, AIX), BSD (FreeBSD, Mac OS X, NetBSD, OpenBSD), GNU/Linux (Red Hat, Debian, Arch, Gentoo), Microsoft Windows (9x, XP, Vista, 7), RISC OS and AmigaOS.
Read more about this topic: LaTeX