Now, download .jad - the java declaration file, from given link.
Now, download .jar file. Back it up. Unpack with RAR, 7Zip or any other program that works wth .rar files. Inside, find META-INF\MANIFEST.MF. Change midlet name - this allows to install several identic apps under different names. Then change text after mdlet-1: this will be the name that will appear under icon of installed app. And last, I changed icon to my avatar. For this, save your avatar as 32x32 or 64x64 .png file.Now, it's time to put the changed manifest back into jar :). You can do it by opening original .jar and drag-n-drop new manifest overwriting the old one. If you changed icon, drop it in the .jar root, nearby or instead of GmailIcon.png.
Now, send your .jar to the phone, install, login, enjoy.You can switch Firefox back to original UA profile.