Are there any craft restrictions to the crew skills?

 

I am wondering if I can be both a Jedi and cyber for the grenades for example.

there are no class restrictions in the skills themselves. Restrictions apply to the products of those skills. It you play sith marauder, you won't be able to equip heavy armor, even if you can make it, for example

But you will be able to use the grenades as a ranged attack as a Sith Jug than.

 

Thanks