Praat is “a free scientific computer software program for the analysis of speech in phonetics”.
The concordancer software ConcApp (version 5) has now become purchaseware. It is an easy to use program recommended for those learning to use corpus and concordancers. Its best feature, though, is that it can be used for not only English and French texts but also Japanese (tested), Chinese, Thai and Russian.
While it is purchaseware it is reasonably priced (USD20 as of posting), well worth it if you are in need of concordancing in languages other than English.