Is it possible to distribute simuations on one machine with one license ?
Most of the time the cpu usage of my simulations is around 3-5 percent ( its a 64 core machine ) so multithreading seems to be quite bad in my scenarios, but what about distribute ? I can start multiple instances of houdini so why not make them work together to achive a better cpu usage …

I don't see why not. Sounds like a good idea to me.

How would I do that ?
Do I have to install several hqueue clients on the same machine ?
Is that even possible ?
Can I use distribute without hqueue ?

Install hqueue client/server on the same machine.

It is not exactly the same scenario but I used to cache 4 to 8 bullet or Solid solvers to utilize dual xeons, and it used to work perfect, although I dont suggest this for Flip or Pyro as they use multithread pretty well