Twiki

Twiki is another wiki engine.

Twiki to MediaWiki

Twiki-to-Mediawiki (January 2017) is a project to import a TWiki web into Mediawiki. It converts basic syntax (including links, emphasis, lists, headers, and tables), imports pages (using MediaWiki maintenance scripts), preserves timestamps and authorship, uploads attached files (e.g. images) and updates inline links to those files, imports the table of interwiki links, correctly handles transclusion and redirects, maps several TWiki variables to (approximate) MediaWiki equivalents, and also includes mappings from several TWiki plugins (EFetchPlugin, LatexModePlugin, DirectedGraphPlugin) to the equivalent MediaWiki extensions (PubmedParser, Math, GraphViz). It's supported by a suite of tests and is derived from the itoolbox.com script linked below (though it has grown considerably since then). Its only dependency is Perl (and, of course, MediaWiki).

Some other programs:

One of the working scripts can be found at ittoolbox.com. It reads a TWiki textfile and spits MediaWiki-Syntax to STDOUT. Perl required.
Converting TWiki to MediaWiki (from April 2005)
TWiki to MediaWiki (September 2005)
Twiki-MediaWiki-Migrate program (last update Aug 2006)

Converting TWiki to FusionForge's Mediawiki (from April 2014) : handles the special case of MediaWiki's integration in FusionForge, for authentication. It uses MediaWiki's API, so could be used even by non-admins.
Converting Twiki to MediaWiki (last update: May 2014): Javascript converter of twiki to mediawiki (includes sample web program)
Converting Twiki to MediaWiki (last update: May 2014): Python converter of twiki to mediawiki (includes sample Flask program)
https://github.com/SRSoftware/TWiki2MediaWiki is a php based script for automatic migration of a whole wiki

MediaWiki to Twiki

See MediaWikiToTWikiAddOn on twiki.org.

There is also initial work on a Twiki plugin to read MediaWiki syntax.