The thing about people who get a bee in their bonnets about open source in this sort of context is that it makes no sense. They want to replace a part that required serious proprietary resources to create, and would be happy to use salvaged or NOS, but balk if you need the odd proprietary tool to recreate them as FPGAs? Even if you require proprietary tools to create the bitstreams there's nothing that stops the bitstream from being freely redistributed, and if someone has problems with shelling out for a $5 third party programming cable then they've picked the wrong hobby trying to fix up old electronics.
Well, the "open source" thing is one thing, and only part of the problem for those people IMHO. Many are just looking for a ready-to-use solution, but fully open-source. Meaning they don't want to do any effort, or are just not qualified to do so (but they seem to think they are for judging they absolutely need something open-source). What that means is, basically something like this can be implemented in a few lines of HDL (say a few tens for a complete solution with all the boilerplate code), and portable enough that it can be synthesized on any FPGA you like. And now some of them are supported by open-source tools, actually, like yosys. But if you don't provide a ready-to-use solution using yosys yourself, many people will whine. Granted, at the time Bassman59 did it, there probably was absolutely no open-source tool for FPGAs, but this is just a minor concern IMO. I'd be willing to bet that if you release something like this today, you'll get a lot of the same reactions.
And it opens the can of worms question, what is open source anyway, when hardware is involved? If you use discrete logic gates, do those guys think it will make it more open source? Are the off-the-shelf logic gates you use open source? They aren't. The line is fuzzy, and people will put it wherever they feel like. It's always going to be pretty subjective, because *100%* open source hardware, if you're considering it on a strict level, does not exist.