gnu: Add texlive-csplain.

* gnu/packages/tex.scm (texlive-csplain): New variable.

gnu/packages/tex.scm

@@ -4081,6 +4081,34 @@ polyglossia package rather than Babel.")
 
 (define-deprecated-package texlive-latex-babel texlive-babel)
 
+;;; Note: if this package is modified, its name must be changed to comply with
+;;; its license.
+(define-public texlive-csplain
+  (package
+    (inherit (simple-texlive-package
+              "texlive-csplain"
+              (list "tex/csplain/base/")
+              (base32 "0cgrwc8lgf2x2hq6bb4kqxw597card985zdd9ipn7k98mmwrxhz3")
+              #:trivial? #t))
+    (home-page "http://petr.olsak.net/csplain-e.html")
+    (synopsis "Plain TeX multilanguage support")
+    (description "CSplain is a small extension of basic Plain TeX macros from
+which the formats @code{csplain} and @code{pdfcsplain} can be generated.  It
+supports: hyphenation of words for 50+ languages, simple and powerful font
+loading system (various sizes of fonts), TeX, pdfTeX, XeTeX and LuaTeX
+engines, math fonts simply loaded with full amstex-like features, three
+internal encodings (IL2 for Czech/Slovak languages, T1 for many languages with
+latin alphabet and Unicode in new TeX engines), natural UTF-8 input in pdfTeX
+using encTeX without any active characters, Czech and Slovak special
+typesetting features.  An important part of the package is OPmac, which
+implements most of LaTeX's features (sectioning, font selection, color, hyper
+reference and URLs, bibliography, index, table of contents, tables, etc.) by
+Plain TeX macros.  The OPmac macros can generate a bibliography without any
+external program.")
+    ;; This custom permissive license includes as a redistribution condition
+    ;; that says the package must be renamed from 'csplain' if it is modified.
+    (license (license:non-copyleft "file:///tex/csplain/base/csplain.ini"))))
+
 (define-public texlive-generic-babel-english
   (package
     (name "texlive-generic-babel-english")