Q: Is it fair use to backup android or iphone apps or other software I obtained legally if not stated in the terms of use?

A: There is no definitive yes or no answer to this question, as determining fair use involves a complex, fact-specific analysis. However, some key considerations regarding backing up legally obtained apps and software include:

- If the terms of use or license agreement specifically prohibit making backups, then generally making backups would not be permissible fair use and could potentially constitute copyright infringement.

- If the terms are silent on backups, courts will examine factors like:

(1) the purpose and character of the use (e.g. noncommercial personal backup likely favors fair use);

(2) the nature of the work (creative works get more protection than functional works);

(3) amount copied in relation to the whole work (backing up entire apps disfavors fair use); and

(4) effect on market for the work (if backups replace need to purchase additional copies, this disfavors fair use).

- Backups that facilitate continued personal, lawful use of software after loss or damage of original copy tend to favor fair use if not excessive copies made. But circumventing copy protection measures could violate anti-circumvention laws.

- Factors like backing up only apps you created or apps no longer reasonably available for purchase could favor fair use.

So in summary, legality of app/software backups involves weighing these sorts of factors. Reasonable personal backups of purchased apps, done solely to allow continued lawful access, can often qualify as fair use, but restrictions in terms of service may control. Consultation with an IP attorney is advisable for particular situations.