I just downloaded and looked at fwrules50.zip.

It appears to be under the GPL. I see no other applicable license. The main copyright holders appear to be Stephan Moser and Sean O'Neill.

IANAL, this is not legal advice. However here is what my limited understanding says.

1. I have no idea whether you have strong legal grounds for complaint. Probably not.
2. If the company is distributing a product based on this software and is not giving source code or telling their customers that it is GPLed, then both Stephan Moser and Sean O'Neill have grounds for complaint. Unlike you they signed no agreement. Indeed it is their copyrighted code that is being used without permission.
3. The FSF is interested in pursuing cases like this. They more than anyone else would like to see the GPL proven in a court of law, and they would prefer to see it happen on a fairly simple case where they are clearly in the right.
4. I have no idea what your rights as a whistle-blower would be. In an ideal world you would have perfect immunity. This is not an ideal world, I don't even know what country you are in, let alone the laws that apply to you. Before raising a case you may wish to talk to a lawyer again with this question. If I raise this issue to the copyright holders and offer to serve as a friendly witness, what could my former employer try to do about it? Only if you are comfortable with the answer should you proceed.

I am deadly serious about the last item. Remember that one of the obvious defences that the company will have is that you are lying, the script was developed independently, and you are lying to get revenge to settle a feud. It will be no problem for them to make up a plausible lie, and no problem to find people who are willing to repeat those lies under oath..