The jar is a bit odd, but doesn't look malicious at first glance.
It appears to be the mysql JDBC driver jar with a few classes added to provide the GUI. (the manifest gives this away).
Gmail believes its clean.
I've inspected the code via decompilation, and it looks clean. standard java Swing gui code.
I haven't gone through all the bundled mysql classes, however.
Might I suggest reworking this into webstart? its not too much work, gives you an easy method to update the tool and lets you split the app up into jar files, so the mysql driver could live by itself again.