I'm not sure what "Juniper free certification" you are referring to. The Juniper website indicates that all written exams are delivered only via PearsonVUE test centres. The only free certifications seem to be the occasonal offer of a voucher or as a way to tempt people with other qualifications (e.g. Cisco) to go for Juniper as well.
In terms of exam taking, I'm in 2 minds on this. I do think there is a lot to be said for having to take the exam in a "sanitised" environment where the candidate has to provide proof they are who they say they are, and have controlled access to materials. However, the closed-book exam is not something I am a fan of; mainly because it is not a real life situation. While you could counter-argue that if you have the manual to hand you could find every answer, you still need to know where to look and also how to find it within the allotted time for the exam. But on the other hand (and I'm thinking particularly about Cisco here) it is very unlikely that you would be trying to do subnetting without some sort of tool - what self-respecting engineer doesn't have a subnetting calculator on his phone (or access to the wonder SolarWinds subnet calculator) these days? At the end of the day, even with the resources you still need to know *how* to use them to get the correct answer and apply the information they supply.
Of course, one of the biggest things this doesn't take account of is experience. Sadly, I've found in the Middle East a lot of weight is given to titles (Engineer being a title they like to use) and qualifications - experience almost seems to be an afterthought, if it is considered at all. I have seen many examples where people have all sorts of qualifications (Microsoft certified people seem to be a usual culprit from experience) but when it comes to a real life situation (and particularly problem solving) they havn't got a clue! I guess it's all a matter of balance - there's the old Catch-22 of how to get experience without a job; how to get a job without experience?