Cray has their own Fortran compiler, so it's quite possible that Bill is forbidden from contributing to other Fortran compilers due to IP issues.
And as you can see from the thread, he's caught in the middle, passing messages between a customer who wants this issue fixed and a team that doesn't want to fix it. That's not a fun place to be - you basically get yelled at by both sides.
If the customer wants something, then you the vendor either give them what they want, or don't.
It's no one else's problem.
There are no "ip issues" preventing an employee from working on a competing product, only from doing so without permission which the employer is free to grant at any time.
This possible issue does not provide any tiniest bit of of excuse, and does not invalidate the critiques at all.
No one is "caught in the middle" in any way that anyone else has any obligation to care about, not even a merely "being a nice and considerate person" obligation.
If the customer wants something, the vendor can absolutely satisfy them any time they want by a number of different means. And certainly this employee is no voiceless intern, is both knowledgeable and empowered enough to inform his employer about those means. If they don't employ any of those means, it's no one else's fault and so no one else's problem.
Bill has no right or ability to compel third parties not involved in the transaction to help him provide that service.
If Bill can't get the job done, that's Bill's problem.
The buck stops with Bill.