Who/what is behind LaTeX?
Citing the CTAN LaTeX entry:
LaTeX is a widely-used macro package for TeX, providing many basic document formating commands extended by a wide range of packages. It is a development of Leslie Lamport's LaTeX 2.09, and superseded the older system in June 1994. The basic distribution is catalogued separately, at latex-base; apart from a large set of contributed packages and third-party documentation (elsewhere on the archive), the distribution includes:
– a bunch of required packages, which LaTeX authors are “entitled to assume” will be present on any system running LaTeX; and – a minimal set of documentation detailing differences from the ‘old’ version of LaTeX in the areas of user commands, font selection and control, class and package writing, font encodings, configuration options and modification of LaTeX.
It's published under the LaTeX Project License 1.3 and is considered to be free and changeable. (See LaTeX Project too)
It was developed initially by Leslie Lamport to ease the usage of TeX
(which was designed by Donald E. Knuth also named The Grand Wizard (not to be confused with the name from the infamous and dreadful KKK) in the late 70s/early 80s)
Although there are commercial TeX versions which have to be paid for the majority of users download LaTeX (and XeLaTeX/LuaLaTeX as well as TeX) either as the TeXLive or MikTeX distributions or directly from the CTAN server.
A list of current maintainers of LaTeX2e
and LaTeX 3
core can be found here: LaTeX 3.
A lot of other people design(ed) additions as style oder class packages, all based on the core -- everybody is allowed to use LaTeX and to provide own additions and formats -- that's one of the most thrilling (and sometimes difficult) features of this 'programming' language.
LaTeX users and developers meet in conferences and are organized in global communities such as TUG (TeX User Group), Dante (a German/Austrian TeX user group) and several other local/national groups as well as online like here on TeX.SX, goLaTeX, LaTeX community and some others.
I would also mention Heiko Oberdiek if only because the incredible Hyperref is really what is getting LaTeX on the Web via pdf. And also whoever MathJax is because it is only because of MathJax that LaTeX mathematics is getting on the Web.