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I have a project with MIT license. The idea of dual licensing came up several times and I wonder if it's possible to add a second license next to MIT that obligates companies e.g. with larger than $1,000,000/year revenue to pay some fee.
I found that dual licensing is usually done with GPL licenses to "unlock" the restrictions of the GPL license but I haven't found any cases for MIT.
dual licensing is usually done with GPL licenses to "unlock" the restrictions of the GPL license but I haven't found any cases for MIT
That's because there are no restrictions in permissive licences that would justify payment to unlock. Taking the part of a hypothetical licensee and hir derivative work, I can see why I might pay to avoid the obligation to honour the GPL with respect to my derivative, as the requirement to make source available under the GPL would weaken my control of my product. But why on earth would I pay solely to avoid the requirement to reproduce the text of the MIT licence and your copyright notice on page 8,752 of volume IV of my manual?
Moreover, the usual "dual licensing" situation involves potential licensees deciding which of the two licences they wish to honour: the no-cost copyleft one, or the with-cost one that allows them to lock their product up. The choice you suggest, however, cannot be given to large corporations, otherwise they'll just choose the zero-cost MIT-licensed option.
You can't have a scheme that offers your work under one of two licences (MIT or paid-for) depending on the revenue of the licensee, because as the CTO of EvilCorp I'll just get my 17-year old nephew (whose annual income is £235.50 and two packets of wine gums) to take a copy under MIT, then pass an MIT-licensed copy on to me.
So what you're really asking about, it seems to me, is whether you can have a single licence that acts like MIT but only to potential licensees whose annual income is below a certain threshold. I'm not very confident that you could, though it is possible: but such a licence would certainly be non-free, and so we can give no further advice on it here.
