AntConc

Available

 * http://www.laurenceanthony.net/software/antconc/

Developer

 * Laurence Anthony, Ph.D., Center for  English  Language  Education  in  Science  and  Engineering, School  of  Science  andEngineering, Waseda University, Japan

Description
A cross-platform corpus analysis toolkit for concordancing and analysing texts encoded in Unicode. AntConc specialises in creating concordances, but the developer's software page provides many tools for other tasks, such as AntCorGen for corpus creation, AntFileConverter to convert PDF and Word (DOCX) files into plain text for use in corpus tools like AntConc etc.

Licence
Copyright Laurence Anthony. Not free open source software, but freeware.