I know that there are branding options available for this but I would like to know if it is “legal” to just clone the repo, change the icon pictures, build it and upload it to the playstore or at least use them internally in my enterprise as an apk. No commercial intensions…
Sure, the app is licensed under the GPL. So the only legal issue in your case is that you are violating trademarks.
Therefore you will need to remove / replace all brands, images, logos etc. from the app and rename each occurrence from “Nextcloud” to your custom name…
Also you will have to change the app ID, since they have to be unique at the Play Store.
Keep in mind, that the license requires you to also publish your modified source¹ under the same conditions, no matter whether you have commercial intentions or not.
Disclaimer: I do not work for nor am i related in any way to Nextcloud Inc… This i no legal advice.
Correct me if i missed something @jospoortvliet
Edit: ¹ This means of course that you have to provide the source code to everyone you distribute the compiled APK - so if you are only using it within your enterprise, you only need to make the source code available within your enterprise but not publicly. If you are distributing the app publicly, you also have to make the changed source code available publicly.
Thank you for the the thorogh explanation.
Stefan was very much correct. You can learn more on nextcloud.com/trademarks - there we describe various scenarios under which you can use our code and our trademarks.