Is there a tool or library to extract data from Mysql database files without having the database engine available?
If you are brave and a little fool-hearty, try this crazy idea:

Since myisamchk can read, write, and analyze MyISAM tables independent of mysqld, get a hold of the source code for myisamchk, take a look around and see if you can borrow any C/C++ code, algorithms, structures, classes, or just any ideas from it.