Having the testnet available to the public is probably the fastest way to get the exchange tested for free, is it a bad idea? Some would argue there will be many who are eager to copy , but not sure how much they can and if thats the case every company has this threat and always the best ones win in the end. I believe a few users were selected before for testing, but opening to public would definitely help with the large number of users testing.
I personally would love to help the testing of NEX but due it being a security it probably requires some more control over it then we might expect. When they first release it will be test environment with limited matching engines (ofcourse for testing purposes) in the future that will be able to grow to a decentralized mature environment.
I’d like to test the exchange
From what I understand the testnet should already be live as that’s what they have been working with stress testing it and getting feedback. Thus, it’s a closed testnet which should already have testers under NDA from what I recall a few months ago. I believe it was select ICO contributors that were selected if they passed the list of requirements. But I could be wrong.
Regardless, I doubt there will be an open public testnet prior to launch.