Install CA without having to activate screen lock
I've written an article on creating &amp; installing CAcert certificates as Android System Certificates (Android >=4.2), thus allowing you to use your device without lockscreen:

http://wiki.pcprobleemloos.nl/android/cacert

Main part of my article:

cat root.crt &gt; 5ed36f99.0
openssl x509 -inform PEM -text -in root.crt -out /dev/null &gt;&gt; 5ed36f99.0
cat class3.crt &gt; e5662767.0
openssl x509 -inform PEM -text -in class3.crt -out /dev/null &gt;&gt; e5662767.0


Copy the files 5ed36f99.0 and e5662767.0 to /system/etc/security/cacerts/ (and chmod 644 them), reboot and it should work. Check Settings -> Security -> Certificates, it should list both "CAcert Inc." and "Root CA". Note that some browsers might use their own certificate store instead of the Android one.

The Android security model explicitly forces you to have a lockscreen whenever a non-system (user) certificate is installed. There is no configuration option around this.

You can either replace your stock Android version with one which has removed this requirement (I do not think that any exist, but you could theoretically create your own).

The other option is using (temporary) root access for installing this certificate, and then 'unrooting' it, although that sounds a bit silly.