Tried it with Raspbian Jessie (RB 3B), and got ca-certificates is already the newest version.
Getting the same error as @Poltergeister and with curl
curl https://openframeworks.cc/versions/v0.9.8/of_v0.9.8_linuxarmv6l_release.tar.gz --output OF.tar.gz
I get this:
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: http://curl.haxx.se/docs/sslcerts.html
curl performs SSL certificate verification by default, using a “bundle”
of Certificate Authority (CA) public keys (CA certs). If the default
bundle file isn’t adequate, you can specify an alternate file
using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
the bundle, the certificate verification probably failed due to a
problem with the certificate (it might be expired, or the name might
not match the domain name in the URL).
If you’d like to turn off curl’s verification of the certificate, use
the -k (or --insecure) option.