There are no caps imposed on the download and upload speeds other than physical limitations of hardware.
Our fair usage policy is documented in our TOS:
We do have a couple of restrictions such as you can not run adult websites, and you can not run your own CDN on top of our servers.
As for anything else we're working with customers on a case by case basis. So far customers aren't abusing our free bandwidth and we would like to maintain that for the future. If some edge cases come up where users are misusing this trust we would update our TOS to take that into account but so far everyone has been very respectful.