Couple things in addition to all the other comments.
The USBs you see on ebay are pirated copies and not official SRS copies. The only digital copy released, was released in the early 2000s, right before the founder died (in 2004). It can't even run on modern computers, it has directions for running MS Dos (that should give you an idea how old it is). I have a copy I treat it as a collectible at this point.
I have heard of there being errors in the USB. But I suppose that's the risk you take with a pirated copy of the original, the quality goes down (as it does with most examples).
Bill Mook was never part owner of the SRS to my knowledge. You may be thinking of Franklin "Frank" Mallory. He did have some help from friends in his though. The main players were Frank Mallory, Charlie Pate and Wayne Gagner (current owner).
The original guys did not want everything for free. The guys who ran the SRS would get irratated at collectors trying to milk whatever they could for free with having to pay as little as possible. Can you imagine spending countless hours pouring through government documentation and people simply take a screen shot of your work and trying to sell for a premium on the cheap? It's pretty low in my opinion.
I was told by a friend of Mallory's he found that irratating, collectors just trying to increase their values rather than appreciating the actual history of it. Which I can understand.
The SRS is almost completely defunct at this point. Which is unfortunate, it's owned by one individual who is in his mid-late 80s. You can imagine how taxing that can be traveling to Washington DC or College Park as you're approaching your 90s. He's a nice guy and I like him, and its unfortunate the state it's in now. Mallory's life work has been reduced to a cheap thumb drive which is copyright infringment. Contrary to popular belief you can copyright data off of primary sources. You're not copyrighting the government document, just the data off of it in the manner you organize it. Which required substantial effort on their part.