The following people or companies have contributed a non-trival amount of code to Aspell and thus own the Copyright to part of Aspell.
Bug fixes and enhancements to word-list-compress.
Wrote the Nroff filter.
Enhanced the SGML filter to also support skipping sgml tags such as "script" blocks.
Wrote MySpell which is a simple spell checker library that supports affix compression. Aspell affix compression code is based on his code.
Added support for loadable filters.
Wrote a locale independent version of strtol and strtod. Wrote the original loadable filter support however his code has been completely rewritten by Christoph Hintermüller and Kevin Atkinson.
Wrote the generic soundslike algorithm which gets all of its data from a file, thus eliminating almost all need for language specific code from Aspell.
Parts of the SGI STL code were used in various places throughout the Aspell source.
In addition the authors of some of translated messages did not release their work into the Public Domain, and thus own the copyright to the translated text. See the files *.po in the po directory for more details.
The following people also contributed to the development of Aspell but do not own the Copyright to part of Aspell.
Added gettext support.
Converted the manual to texinfo.
Wrote the original metaphone algorithm; however, he released his work into the Public Domain.
Converted the metaphone algorithm into C code and made some enhancements to the original algorithm. He also released his work into the Public Domain.
The authors of Ispell. Many of the ideas used in Aspell, especially with the affix code, were taken from Ispell. However none of the original Ispell code is used in Aspell.