I am not sure if this is the right place to ask, but is there a free-to-use licence for audio samples like drum-kit sounds? And what if I want to use the samples in a commercial application? And what if I produce the samples on my own, using a commercial software, will the samples be free then?
If I understand your question right then you are looking for samples to use in a commercial application.
There is a big difference between purchasing the samples and creating them yourself. As far as I know if you create any sound using commercial software then the end result is your own. Eg if I use Cubase to record and release a song then Steinberg have no claim on the song, and likewise if I use a particular synth or sample library to create the work. I know this gets curious when it comes down to for instance someone trying to re-sell on actual samples from a synth or library which I presume would be a breach of copyright, so you would have to estimate where you stand on this I suppose and get legal advice if necessary.
On the other hand if you want to use samples directly in a commercial application, like a game for instance, then the usage would be covered by the licence agreement. In general I know more about other elements like photos and pieces of software but I suppose samples and clips are similar. In that regard there would be 2 licences, and this is the case for instance with Audio Jungle . The typical licence allows for normal usage then as far as I know the extended licence ( which is many times the price of the standard licence ) allows for you to include the file in something you are re-selling. But there will be limitations to this so you would really need to research it pretty well and to be sure to be sure you'd need to get the info direct from the licence holder.
In general if the licence is not clear and easy to follow ( and get clarification on ) then it's probably better to look elsewhere.
I would say you are probably in no danger of getting sued by any of the DAW manufacturers if you create your own sounds on their software though.
If they are 'free to use' like those samples that you can buy from loopmasters, producerloops etc. then they are exactly that unless stated otherwise. Most bought samples come with a license agreement that should explain how you can use them. It depends where you got the samples from as license agreements can differ between suppliers.