Hi. You might want to add a couple of items to the Java FAQ that aren't currently there, though there's some discussion in the forum:
1. jikes works very well for compiling java on my C750. I use it all the time.
2. MySQL also works very well, and communicates with java programs using jdbc just fine. I can also run the MySQL client GUI on my laptop and connect to the Zaurus MySQL server using wireless cards. I can even export databases from MSAccess on my laptop directly to MySQL on the C750.

You can see some examples in