From Seo Wiki - Search Engine Optimization and Programming Languages
|Original author(s)||Bruno Haible and Michael Stoll|
|Initial release||April 1987|
|Stable release||2.48 / 2009 July 28|
|Available in||Common Lisp|
|Type||Compiler and runtime|
|License||GNU General Public License|
In computing, CLISP is an implementation of the programming language Common Lisp originally developed by Bruno Haible and Michael Stoll for the Atari ST. Today it supports Unix and Microsoft Windows systems.
CLISP is an implementation of Common Lisp, including an interpreter and a bytecode compiler, as well as a debugger, a socket interface, a high-level foreign language interface, strong internationalization support, and object systems (CLOS and MOP).
Haible did not originally intend to distribute CLISP under the GPL, but in a well-publicised email exchange with Richard Stallman, he eventually agreed to do so. The issue at stake was whether CLISP was a derivative work of the GNU readline library. 
CLISP is extremely portable, running on almost all Unix-based operating systems as well as on Microsoft Windows. Although interpreting bytecode is usually slower than running compiled native binaries, this is not always a major issue (especially in applications like Web development where I/O is the bottleneck).