Connectix

Decompilation is not automatically illegal.

He points to Sega versus Accolade and Sony versus Connectix, where reverse engineering was treated as fair use when needed to access unprotected functional elements for legitimate purposes.

But distributing a reconstructed version of a copyrighted game is a very different matter, and, and most end-user license agreements forbid reverse engineering.

So no, this does not mean all software is now open source in the licensing sense.