Minecraft is the second-best-selling computer game in history (behind only Tetris), and has 91 million active players (though, yes, a fair number of those are kids). I think it fails the “obscure-ish” test pretty spectacularly, especially when compared to some of the other nominations in this thread.
Did anyone ever buy mIRC?
No, not at all. Less pedantic and actually meaningful point: it’s not like Alphabet was some huge existing conglomerate that decided to buy Google. It was created by Google as part of a restructuring precisely to reflect their diverse lines of business. That surprising degree of diversity which arose from the original search engine business is precisely what I’m remarking on.
You are of course correct that for technical and legal precision I should have referred to it as “Alphabet”, but around here where the Sidewalk Labs project is big news it’s always referred to as a Google initiative, mainly because to most people “alphabet” means your ABCs, or possibly your soup. 
On the other hand - didn’t make it into the OP despite being a much better example of what the OP is asking about than the things that *did *make it into the OP (getting a lot of money for writing a specific program, not for running a successful company)
How about Peter Norton? Back in the day, when even I could keep up with computing, I carried a copy of his ubiquitous Norton Utilities on a floppy disc in my pocket to recover the files that secretaries accidentally deleted.
Granted, the guy apparently made a huge sum of money for one specific program, yes. Just not an obscure one, in the slightest.
Google’s business model is selling targeted advertising. Every service and product they offer revolves around being able to collect more data about people so they can sell more accurate advertising. Search tells them things you’re interested enough in to go looking for. GMail lets them see what you talk about, any shopping invoices you get via email, flight confirmations, etc. Android allows them to follow your mobile web browsing closely, track your location at all times, and steers you into their other services like Google Search and GMail. Youtube tells them what kind of video content you’re interested in, which says a lot about you. If you’re watching home improvement how-tos, you’re probably thinking about renovating your house. If you watch clips from the Simpsons, they know that you like that show and similar.
They’re interested in SideWalk labs because the smart technology they want to install will allow them to better track people’s movements, so they can see what stores they pause to window shop, etc.
I saw this and thought serial attached scsi. Commonly abbreviated SaS
I worked for SAS, they are well known in the field of statistics they are the leading system for statistics . They are big in clinical trials and health research areas but also in banking. Both the founders are billionaires and I visited one of their houses. It is a big house but not fancy, just a typical house other than it is 10,000 square feet.
Since the OP said exploited Walmart was the first retail store to track inventory with computer software. They use a program called Retail Link to manage its suppliers and inventory. The heirs of Sam Walton are worth a combined 140 billion.
Anything that’s made $billions by selling individual licenses to normal people for tens of dollars each can’t possibly be obscure as far as software goes. Sure, not everyone has bought Minecraft, but a movie that grosses $1 billion isn’t obscure either, just because only like 3% of the population has seen it.
I like SAS or SAP as an answer. I’m a software developer and while I’ve vaguely heard of them, I couldn’t tell you what they do.
I have a hard time recognizing SAP as “obscure”.
Its just an ERP (Enterprise Resource Planning) software. Think of it as a much more complex Quickbooks. If you’re running a business out of your garage you maybe buy a quickbooks license. If you have millions to spend on implementing the software that your business uses to record financial transactions and track other business data, you buy SAP (or one of it’s competitors).
To be fair, i work in corporate finance/accounting, so maybe i’m biased.
To me, obscure is more like software people use everyday that does stuff in the background so most end users don’t even know they’re using it.
I think they were both pretty obscure to non sysadmins/programmers.
And your link for Trumpet Winsock the same link you quoted from me. 
But point taken on Trumpet Winsock not making a lot of money. I figured it did, but the link says otherwise.
I can’t imagine the pkzip people made any money either; they released their file format into public domain in 1989, so anyone with the programming chops could make their own zip file encoder/decoder, and many have.
And Clawdio; you’re looking at a very narrow, accounting-centric view of an ERP system; for many organizations using them, it’s the “other business data” that is really the heart of the thing. It’s a whole lot more than just a steroidal Quickbooks.
ERP systems let a business integrate their inventory, production processes, accounting, purchasing and planning in one system. So for example, if you place a customer order to produce a widget, that’ll do a whole host of things- create a work order to build the widget, allocate inventory, log accounting transactions, potentially set up ordering new inventory, etc… So that at the end of the day, everything is in sync- you have say… 4 less of some inventory item in stock, one widget in WIP, accounting entries for the widget and inventory items, a customer order (AR) for the widget, and possibly a purchase order and associated AP entries and pending inventory entries.
SAP is probably one of the biggest ERP providers along with Oracle, and probably even less publicly known- Oracle at least puts their logo on yachts and stuff, while SAP is some weird-ass very quiet German company that nobody knows much about. Hell, I’m aware of SAP, work in a group that deals with it daily, and am familiar with ERP systems, and had to look up what SAP stands for. (“Systeme, Anwendungen, Produkte in der Datenverarbeitung”, or in English, “Systems, Applications and Products for Data Processing”)
Oh i’m right with you. I’ve essentially made a career out of understanding & interpreting the data that is available in SAP. I was just trying to give a simple one line explanation to the folks not familiar with it, though you probably did a better job in your short paragraph.
I still don’t consider it obscure though. For a while there, i seem to remember seeing national ad campaigns on TV (i think maybe even a Superbowl commercial?).
I don’t work in software or accounting, so I only became aware of use of the acronym ERP in that context within the past couple of years. I’ve been active in the role-playing communities in various MMORPG computer games for years, and it has a very different meaning in that context:
ERP = “Erotic Role-Playing”
Judith Faulkner founded Epic Systems in 1979. Epic is still a privately held corporation, and has never acquired any other companies. Epic does health care software; reportedly 65% of American medical records are on Epic systems. Faulkner is worth 3.something billion.
Not sure exactly how much money it made individuals, but Citrix is one of those things that gets a lot of use without a whole lot of people knowing what the heck it is.
… The Statistical Analysis System marketing people must be a little pissed off about the Software As A Service marketing people …
I knew one of those guys where computers got infected by an early boot-sector virus, and thought “I need some software to clean this up. And prevent it happening again”. He eventually sold his company for enough to retire wealthy, otherwise you might know his name instead of Mcafee. Then his wife died.
Steve Johnson and Chris Grace wrote a compression algorithm that made it possible to transmit image files over low bandwidth, and sold the company to AOL for $1.6 billion in 1996.