You can prevent NukeAssist from launching the Frame Server process, and therefore from requesting a full Nuke license, by launching it from a command prompt or terminal with the --disable-nuke-frameserver argument. The full commands to run are below.
cd "C:\Program Files\Nuke11.0v2\
Nuke11.0.exe" --nukeassist --disable-nuke-frameserver
./Nuke11.0 --nukeassist --disable-nuke-frameserver
./Nuke11.0v2 --nukeassist --disable-nuke-frameserver
This issue is logged as bug 313627 in our system. You can follow the progress of the bug on the public bug tracker at the following link:
313627 - NukeAssist 11.0 always runs FrameServer process in the background so it requests a regular Nuke license (nuke_i) too