Nope -- its still someone's copyright and very possibly trademark. IP law has very little to do with whether any entity is actively using a piece of IP or not, and you can't assume that IP is freed just because that entity isn't around any more. The IP always goes somewhere -- someone acquires the assets either by purchase or inheritance. IP protection only really goes away under four scenarios -- 1) the author explicitly gives it up 2) the term of protection expires 3) a regulatory body or court rules that it doesn't meet the standard necessary to receive protection 4) the IP holder fails to vigorously defend said IP from infringement and it becomes defacto public domain.
Be aware that #4 is not your golden loophole. It doesn't mean that the first movers to start selling unlicensed Mickey Mouse tees get away Scot free if their numbers simply overwhelm Disney's army of lawyers, it means that if, at some point, Disney simply gave up defending that IP, they can't come back years after the fact and start demanding payment from those who've pilfered their IP.
Yes, people sometimes make fan-games, mostly without explicit permission, but sometimes with. Whether or not the fruit of their work is released for free or commercial purposes has no impact on how enforceable the IP is, whether they can seek financial damages, and even very little to do with how much financial damages a plaintiff could seek. These kinds of projects, without permission, are illegal strictly speaking (save few exemptions); they don't charge for their product because doing so would guarantee that their infringement and damages would be pursued, not because being free inoculates them from their potential liabilities.
Standard Disclaimer: I am not a lawyer, and if you desire to attempt navigating the finer points of IP law, you really should hire one who specializes in such.