If you are going for a decompiler, I'd recommend jad. I used it couple of years back. I recall that it had plenty of command-line options and is very efficient too. In addition to legal restrictions, you may encouter other irritants such as obfuscators. Obfuscators juggle up the class file so badly that the source you obtain by de-compiling is hardly readable. Good luck with your de-compiling!
Ganesh