Hi,
what are some open source bitcoin exchange scripts like blinktrade, how these guys actually making money ?
Usually, people making open source programs don't really care about the money or they are doing it for the community/to build an online reputation/portoflio etc...
We don't have much bitcoin exchanges that are open source, some people might think It's that easy to build one but It's not (and It's not to use one that is already open source) because there are a lot of security measures that should be taken and the least error could lead into a disaster and getting users funds being stolen and the fact that bitcoin transaction are irreversible make this even worst, not to mention the fact that those open source scripts might have backdoors and someone without proper programming knowledge shouldn't use them.
I guess you could take PEATIO a look:
https://github.com/peatio but you should know that the development is inactive as the last commit was in October 2015.