One post below might be a bit misleading -- it's just 18 Msps, not 100 -- so think of it as good for signals up to 1 MHz or so with decent fidelity... And it uses a PIC32, not STM32. It is 12 bit ADC, but the noise floor makes it more like 10 or 11. A cool thing is it also does digital capture and waveform generation at the same time, but clearly it's all pretty simple...
My goal was to be able to get these in a classroom at every seat, where there's already a computer or tablet or chromebook, and have it "just work"... The thing I like the best by far, though, is javascript access -- you only need a webpage for the GUI -- no software install or app store or anything!
To go deeper for the classroom experiments, you can use a different "deep dive" webpage with a command-line UI and log in interactively and take control of all the pins programmatically in BASIC, and even configure the board to autorun a BASIC program on power-up... You can make a "simon" game with 4 switches, 4 LEDs, a buzzer, and about 100 lines of code... Or with a thermocouple and an op-amp and a solid-state relay, you can make a cool toaster oven temperature controller for reflow soldering -- which is how I built all the prototypes... The nice thing is the javascript access on the host comes for free still, and so BASIC can talk directly to the host computer (e.g., running python or powershell)! Examples are here: https://rtestardi.github.io/pages/
I have also had fun with automotive applications for Flea-Scope -- it is so easy to just bring out a phone or tablet and measure a crankshaft sensor -- and without it you're just guessing and replacing components from some diagnostics flowchart...
As for licensing, it is all open source, and anyone can rebuild it (and even sell it). There is a patent on the internal BASIC, but there is also a perpetual license to the software builds I have made and tested and released -- conceivably you could build the scope without BASIC at all -- it is unneeded except when you use the board in "deep dive" mode for BASIC programming.
If there is interest, I have toyed with the idea of making a Mosquito-Scope, with 2 channels and selectable input amplification (for sub-millivolt signals) based on the still-brand-new dsPIC33A, which is actually cheaper and faster than the PIC32MK.
-- Rich