The way the github seems to talk about browserstack, it says that it's necessary to utilize testswarm. However, from what I've been reading it seems to just create virtual users/browsers to run all of your unit tests. It looks like you could still use testswarm even without an account, but I haven't seen many resources online about this.
TL;DR: If I set up a computer to just use testswarm to run tests for the browsers it has open, can I do that without having a browserstack account?