Disable the lock screen when specific apps are active?
This can e.g. be realized using Tasker (in fact, I'm even using it that way for "prolonged screen timeout" with reading apps):


Condition: App (opens a popup to select one ore multiple apps, chose the ones you want to act upon)
Task:

Keyguard (disable)
Display -> Timeout (optionally increase display timeout)



The tasks would be executed as soon as one of the selected apps is running in foreground, and reverted to what it was before as soon as the condition no longer is met.

Note: I know that Tasker doesn't come cheap (~5 bucks), but it's worth every cent. To "try before buy", visit its homepage, where you can download a 7-day-trial.