I do like bitcoin (the currency and the software project) but I agree that cryptocurrencies in general almost always means scam.
Personal preferences aside I don't think you can earn much money mining with the CPU nowadays. Is the mining intended to be performed with the GPU? Aren't the binaries to heavy to be CUDA accelerated?.
Please also consider other ways to raise money (not as alternative but paired with opt-in GPU mining).
For example Graeme Gott has paypal links in the download page of his programs: see, for example,
https://gottcode.org/focuswriter/
There's also Ardour, which releases GPLv2 software but whose binaries are paid. They provide different options, please take a look at the form in
https://community.ardour.org/download. Probably it cannot be applied to calibre as is, but I'm sure it worth look at the options they provide to figure out if there's something to borrow
