No you are not pay for the full plugin again, you just pay a small fee for the next release but the milestones versions are free update.

Ok thank you for your answers, but let me clarify what's the problem. I'm making my template using ajax.
Everything works ok, but some components needed the page to be refreshed.
I solved this problem by putting them in iframe and refreshing it's content, but I can't do it for simple-gallery.(when I click on a photo only iframe becomes black, and some photos are too big - so it looks stupid).
What scripts should I include in my template to make simple gallery functioning well, without refreshing the main page.

May be you should have done that from the start so people know what you are talking about.

The pro plugin has worked for me. thanks for the help.