There's one point that I keep bringing up with regards to the OGL.
How do you make it work with the DDI?
Right now, even though we haven't had a new WOTC product in over a year, they STILL have around 80000 subscribers. That's somewhere, as a was mentioned, between 5 and 8 million dollars a year. That's HUGE in a market that's only worth 30 million dollars total. WOTC controls between a quarter and third of the entire market with a single product that costs them virtually nothing to keep running.
If you go with an OGL PHB, an entirely open PHB, it will take about a week before people put up free character builders and whatnot. We saw that before. Within a month of 4e coming out, you had for pay character builders going up. They got shut down, because the GSL doesn't allow for that. But an open 5e? That just opens the floodgates.
Now, how many new PHB's do you have to sell in order to make up the losses to the DDI and the steady revenue stream that represents? How do you have an open 5e and still protect that cash cow?
What you do is what Wizards should have done from the start. You create an API to the DDI database, with authentication for DDI subscribers. You also create a system that allows DDI subscribers to sign up and pay for third-party services. Then you encourage third-party developers to target your API and benefit from a) a back end already built and ready to go, b) up-to-date stats with errata applied, c) access to Product Identity material, and d) Wizards handling the nitty gritty of charging credit cards and managing subscriptions. (Have you ever worked with credit card processing systems on the Web? I have. It's a huge pain.)
And throw open the doors! As a whole, the D&D fanbase is creative, slightly obsessive, and very tech-savvy. Inside a month they'll create better online tools than Wizards has ever been able to build, and most of them will require a DDI subscription. Sure, you could just build your own database of open material without recourse to the API. But why take on the hassle of keeping it up to date, scrubbing it to make sure there's no Product Identity stuff, and handling your own authentication and billing, when you could let Wizards take care of all that and focus on making your app the best it can be?
End result: Wizards gets the goodwill of being "open," a bunch of highly motivated and talented developers working for free to make DDI better, and the DDI revenue stream continuing to flow.
(Now, this approach doesn't require an OGL. It could be done under the GSL or an even stricter regime. But going OGL wouldn't undercut it and might encourage it.)
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