Just out of curiosity: what do you mean to achieve by modifying that .jar?
When you first connect there is usually a message from dropbear/SSH that says
Code:
Rootfs is mounted read-only. Invoke mntroot rw to switch back to a writable rootfs.
That should let you have full reign
The specific file or folder may also be immutable if that does not work
and see if you see a lower case "i" in the results. If there is you can then remove the attribute with
Code:
chattr -i <dir/file>