The use of Javascript on this site will not impact your security. The BlackBox Market is a legal service. Javascript is used to enable client-side encryption which ensures this server's databases record absolutely nothing that can be read. All code sent to your browser is fully open for inspection by reviewing the source of the page. If you are concerned about security, review the source of a page regularly and note any changes. To enable an effective hack, machine code must be injected by a compromised function in javascript and this is relatively easy to spot. It is also architecture specific. See here for further details (Clear Web): http://www.wired.com/threatlevel/2013/08/freedom-hosting/.
Insertion rates have been dropped to 0.02BTC due to the current high value of Bitcoin.