Mobile devices support is in mind since long time but the urgency of other functions is much more important at this time to cover more functions and usability for the erp…
Also I think it would be more suitable for you to use the app from app store or play store, its not much different than the browser because it’s a plain container that actually opens the web version but still it’s a bit better than the browser because of comparability requirements…
The actual app of erpnext MOSTLY will not be open source due to security and copy right concerns…