The relevant packages needed in order to run Java applications under OpenSlug have not yet been placed in the relevant ipkg repository, so simply using the ipkg command will not work.
Instead, a workaround around is possible by downloading the relevant packages from the Unslung repository to the slug and using the ipkg command in file mode.
Followed by the dependent packages :-
Then, use ipkg to install the packages from the file system in the following order :-
You should now be "good to go"
Curious, for me this worked out of the box, just using ipkg to download and install everything./August
ipkg install http://fullurl/fullpackagefilename.ipk(approve sites) works just fine you can even copy the url from a browser and paste into a ssh session http://ipkg.nslu2-linux.org/feeds/unslung/cross/
2009-04-14 Current available packages (and dependencies) needed to install Java are
If packages are missing, they are probably replaced with newer versions. Just check the current available packages at http://ipkg.nslu2-linux.org/feeds/unslung/cross .