1) i purchased woodmart theme there is a license code. I already used this one site. If i use this theme on another site, I just use one demo on my previous site right? so in another site i will use another demo. should i purchase again the theme?
2) there is any option to buy another license? or i have to buy full theme again?
As I mentioned in my previous reply. You should not use the theme because you will not be able to receive automatic updates, and the premium features like demo import and maybe other features will not work properly.
You can use one license code for one domain only. If you want to use the theme on another domain then you need to buy another license.