Hi,
I am in the middle of a project, and I really would like to test all the new features of H17,
but I am a little anxious to do that because I'm not sure that I will be able to use H16.5 and H17 with the same license.

Will I be able to ?

Yes, you can run older versions of Houdini with newer licenses: www.sidefx.com/faq/licensing-trouble/#faq235

Here is what you can do: Install Houdini 17, making sure to leave Houdini 16.5 installed. You should upgrade your license server (choose the “Commercial License” option in the installer), but you do not need to if your current license server (sesinetd) is version 16.5. Once you have installed Houdini 17, run the license administrator and install your Houdini 17 license(s). Then you can run both Houdini 16.5 and Houdini 17.

thanks a lot