In Greek mythology, Procrustes was a rogue smith and bandit. He had an iron bed, in which he invited every passer-by to spend the night. If the guest was shorter than the bed, he used his smith hammer to stretch them to fit. If the guest proved too tall, Procrustes amputated the excess length; nobody ever fitted the bed exactly. Procrustes continued his reign of terror until he was killed by Theseus.
The number of keys is almost always 88, no matter that the lowest notes and the uppermost octave is rarely used. In fact, Mozart's forte piano had only 66 keys, and the keys colors were often reversed. Today, we can find instruments manufactured by Bösendorfer with 92 Keys and even 97 Keys, but other examples are rare.
But the worst arbitrariness is the keys size. As Lionel Yu explains, this is the Piano's Darkest Secret. It is not just the size of the hand that greatly influences performance, given the standardized size of the piano keys, but also may be the cause of musicians' serious injuries or physical disorders. Linda Gould tells his experience with narrower keys in My Piano Has a Secret. There are smaller size violins: 1/2, 3/4 adapted for young people; Why there are not smaller size piano keys as well? This is exactly what the Pianists for Alternatively Sized Keyboards organization is advocating: "If everyone plays the same size, most are playing the wrong size!".
I would like to be able to contribute more to making things better for pianists, but what I can do is making VMPK as flexible as possible. You can configure the number of keys as you wish: 25, 49, 88, up to 121 keys for ten octaves maximum (MIDI has a limit of 128 notes). You may also choose the initial note, and of course the octave shift (base octave) and transposition in semitones. The colors of the keys are also fully configurable, and the key size is the easiest thing: you only need to stretch or shrink the program window to adapt the key size to your taste and needs.
I've just published a new release of Drumstick Libraries 2.6.0 and VMPK 0.8.7, focused on fixing bugs like the handling of low level computer keyboard events (which wasn't working on Wayland before) and touch-screen events on Linux (Wayland and X11). The program can handle as many fingers as the touch-screen supports, but I've noticed that Gnome 41 on Wayland has built-in gestures with three fingers that can't be disabled (or there is not yet an extension/tweak to do so), and those gestures are the cause that you can only use two fingers on VMPK. Sorry!