Letsencrypt (https://letsencrypt.org/) service which is sponsored by a lot of big names like Mozilla and Facebook offers free SSL certificates. I have used it and it is not to difficult to setup and works quite well.
In case of doubt, changing to https would reduce the server throughput and cause more frequent congestion. Edaboard http server performance is already worse enough.
Well, I don't think that HTTPS is necessary. As for the security, you should NOT use the same password on every site, or just make your Edaboard password unique.
Can you please confirm whether it has actually increase load or congestion and reduced the server throughput? I am just curious (extra cost for security)...