Hi, I'm just a user like you, but I think I can help you:
Yes, you can use Brook+ without buying the hardware, however it will perform much slower.
Brook+ can use two computation backends, one for GPU and another for CPU, you can switch
to software mode just setting the environment variable BRT_RUNTIME = CPU
As a warning there are a few cases where the results may differ because Brook+ is
still under development, however they will be eventually fixed.