No, you are just limited to one app and instance at a time. But this should be more than enough to host your average website that gets a couple thousand hits a week.

From the FAQ (not sure if you can access it without being logged in though):

"Will you offer a free version of hosting?

Yes. You get one free application with one instance for 6 months. If you have one app that is using the free instance, you can delete it and you'll be able to create another free one to replace it."