it is possible to create paid apps in nextcloud?
I haven’t seen any paid apps so far. Do you want to build a business around certain apps or do you just seek some sort of financial appreciation of your contributions? For the latter one, some users might be willing to give a financial contribution to obtain an interesting feature.
The question really is if you want to from a business model perspective. It’s probably easier to create a free app and sell mobile integration on the relevant store (e.g. Android/iOS clients) or sell some sort of support for companies like collabora does in the form of readily available docker images or hosting.
Btw, you could also test the waters by creating a kick starter campaign to see if anyone at all is willing to pay for your idea plus you get the benefit of actually selling something before you begin.
from my experience, a donation button in github is at least not working. no feedback at all for me yet
Bountysource at least does work a fair bit, you can see activity here: https://www.bountysource.com/teams/nextcloud
If your app is in github.com/nextcloud/ it is easy to add it to our bountysource and if you ping me with issues you’d like to promote I can direct some of the money we get from people who ‘just’ give it to us to those.