I have three questions:
Whenever BJS team fixes a bug with a PR and closes the ticket - how can I get hold of the fixed version?
Is it true that the fix is immediately available in the playground, although the PG displays the latest released version?
Is there a way to use BJS from source? So to run master with the latest fixes?
Thank you very much,
. Jörg
It will be in our cdn the next day and deployed to npm once a week at the moment 
@RaananW can confirm I am not saying anything wrong
This is correct. we update once a week (thursday morning PST)
Other alternative is to simply fork from master which is always up to date
If you want to run from master you can check the guide here: Start Contributing to Babylon.js | Babylon.js Documentation (babylonjs.com) and of course if you have any questions or run into trouble along the way you can ask for help here 