Font use

[Anonymous]

I would like to know if the fonts included in sketchbook are free for commercial use

[david.lau]

The fonts are part of the OS for iOS/Android.  So yes, it is free to use in 'commercial' products.  

On Windows/Mac, the license is based on the agreements from where you have downloaded them from.  There are many sites that are 'free' but I have not read the licenses for them.  i.e. https://www.1001freefonts.com, https://www.dafont.com