TeXShop is a free LaTeX and TeX editor and previewer for OS X. It is licensed under the GNU GPL. It was developed by the American mathematician Richard Koch. TeXShop was modeled on NeXTstep's bundled TeXview.app and developed for the then new OS X user interface Aqua and capitalized on the native PDF support of that version of the Macintosh operating system, which was itself based on NeXTstep's successor OpenStep. Mitsuhiro Shishikura enhanced it by adding the ability to transfer mathematical expressions directly into Keynote presentations. Lacking the TeX eq -> eps Service which TeXview afforded, other apps such as LaTeXiT.app were developed to provide Service support. TeXShop requires an existing TeX installation and is currently bundled with the MacTeX distribution.