Do they? If you're the one developer in the world keeping their tech going, and the nearest next developer is 6 months of ramp up time away (plus the time for the hiring process), you'd have some leverage.
In this hypothetical scenario, the developer has no leverage to renegotiate, because they have no job options outside of OmniCorp, hence, no BATNA (best alternative to negotiated agreement). If the developer was homeless or independently wealthy, and not in need of a job, they might have the ability to terminate the agreement without reaching a new one. Then the company would truly have something to lose.
But OmniCorp knows that the developer has to pay rent, and no other company is going to offer them anything but an entry level job, because the only experience they have is OmniCorp this, OmniCorp that.
It may seem far-fetched, but believe me, this discussion is hitting close to home for me. My team is currently moving to a highly customized tech stack that is open-source, but has zero or near-zero adoption outside of the company. It's scary; I've been in software for eight years and I feel like I'm fresh out of college. If you're in software I hope it never happens to you.
It happened to me. I got out of it by studying open source tech stacks and building side projects until I could get a job away from the proprietary stuff. It wasn't ideal, but I managed to pull it off.
I'm mostly playing devil's advocate with my replies. It's generally better to stick with mainstream -- and ideally open source -- tech. But I don't entirely agree that proprietary tech is only beneficial to the company in these scenarios. They are taking risks that the employee can take advantage of. Heck, for me, that proprietary company still contacts me on occasion to see if I'll come back.
dont forget, when you can easily apply for 1000s of other jobs, they can also easily find 1000s of ppl out there to replace you. and as far as OmniCorp goes, you know how much IBM is paying now for one of their mainframe programmer? those guys... you lose one, you wont get another.
