http://www.purl.org/tcl/home/man/tcl8.4/TclCmd/load.htm
Clif Flynt has made available a useful C extension to load shared libraries that don't know anything about tcl's _Init function.
The extension allows one to invoke dlopen to load libraries that do not have Tcl entry points (for use by other things that do have legitimate foo_Init entry points).
The dlopen extension is available at:
http://noucorp.com/cgi-bin/noucorp/generic.tcl?dir=/home/httpd/html/tcl/utilities
It's a minimal, single C file extension, but it has been known to work on both Windows and Posix (just retested on Linux)
Tcl syntax help - Arts and crafts of Tcl-Tk programming - Category Command