[...]
[... Jet ...]
"MDB Tools is a package of libraries and utilities that allow Unix-like systems to natively read Microsoft Access database (MDB) files." http://www.sourceforge.net/projects/mdbtools/
A simple way to interact with Access is via CSV files (see also the links there) - plain text files with comma-separet values (in German locale, Access does not allow to use commas though, because it is considered decimal separator, so use semicolons instead; Excel accepts commas though... (RS)
"Jet" is Access's persistence back-end, and the aspect of Access most likely to interest Tcl developers immediately. Win* has bundled Jet for several years now--write a Jet-dependent application, and it should work fine on any Win* host (since Win95?).
'CEPT that now, in 2002, MS has changed the name again, this time from "Jet" to "MSDE". [L1 ] might explain more ...