How oftern new versions are releasing?

Not very often. It depend on libraries (coroutines, korlibs/klock) updates and on some new awesome, but lightweight, features coming.

Where this library could be useful?

First of all, this library will be useful for long uptime applications which have some tasks to do from time to time.

How to use crontab-like syntax?

In two words, you should call buildSchedule or createSimpleScheduler:

buildSchedule("5 * * * *").asFlow().collect { /* do something */ }

You can read more about syntax in String format section.