this two questions are kind of related, so i’ll answer the second part first.
basically in 3.0+, patches are now able to draw arbitrary graphics to the 128x64 screen, using various new api calls the screen.
(many of the other changes are to do with how patches are started etc, which are not really relevant to rPI/PiSound)
the primary problem (esp. as a community endeavour) is that the rPI/PiSound does not present a ‘common platform’… whilst one can argue you could use midi controls to replace the knobs.
it lacks any kind of solution for the display.
the only common solution that exists today would be to use a HDMI monitor/screen.
but thats pretty bulky for what only needs to be a 128x64 screen, so its not something Im interested in.
of course, you could design some hardware yourself that uses one of the freely available oled displays, its not a difficult hardware project, then you could write an interface layer to that.
its not that difficult a project, though you probably need to be able to at least read C++ code, to be able to check the Organelle implementation.
the reason I’ve not been interested in this, is few users would have the necessary hardware to run it, so its of limited appeal to a community.
there are some other projects, that are working in this area - though none are released yet, i don’t know if they are weeks or months off.
btw, none of this is a criticism of the rPI nor PiSound, its just these are DIY solutions, they kind of expect the user to build upon them, to build something tailored to their requirements, to use what they have.
whereas the Organelle is a fixed format, an instrument… so you can easily develop for it, since you know even user has the same thing.
it was this lack of a common UI for cross-platform development, that led me to create Orac.
Orac takes a different approach, its says the common thing between patches is that you have a bunch of parameters - and then leaves it up to the platform to decide how to deal with these.
(hence we can have a remote interface on the rPI, and let it be ‘headless’ still - which is what every piSound owner has 
)
What is your ultimate goal?
if its just to have more patches, or more capabilities…
you could look at moving some of the Organelle patches you like to be Orac modules - this I’ve documented pretty well already.
this would be a community effort that all Orac users could benefit from, on PiSound, Organelle or other platforms - this only requires some basic PD experience, and there are a number of developers already doing this… so a community that could help you.
if you’re a low level coder (C++) , then you could also contribute to the development of Orac.
as for using open source code… thats what its there for.
just respect the license terms (read them!) , and make sure you credit and link back to the original project.
depending upon what you’re exactly doing, will depend on the best way to proceed.
), but at least those four screenlines.
despite I think the organelle is a bit expensive.