The JSmooth licensing is a bit sophisticated, but has no constraint on
your own software.

First, a small executive summary:

- Jsmooth is GPL, but wrappers are LGPL so that there is no constraint
  added to your own code.

- Regarding the executable: there is no restriction on the executable
  generated. You can do whatever you want with it.

The full details are below:

- The overall JSmooth package itself is GPL. Any work based on it,
  specially but not limited to, the full-java executable generation
  code, is GPL. In other words, if you create derivative work using
  jsmooth, it has to be GPL as well.

- As an exception, the Skeletons (all the C++ code from jsmooth) used
  as a basis to create the launchers are LGPL. They can be used by for
  other programs, or can be linked with, as LGPL. In this case, there
  is no constraint on the licensing of your own program, but you must
  mention the LGPL and provide a pointer to the jsmooth skeleton
  source code.

- As an exception to the exception above, the executable generated
  (the launchers created by JSmooth) are under the LGPL with a
  "runtime exception" similar to the gcc licence exception: It is not
  required that you distribute the source code with, nor that you
  publish a notice mentionning jsmooth. It's not far from
  public-domain, but the LGPL warranty-limitation still applies.