Strong Copyleft licenses other than the GNU GPL family.

[Mario Castelán Castro]

Hello.

Apart from the GNU GPL GNU LGPL, GNU AGPL, and Affero GPL, are there 
other *strong Copyleft* licenses (note that this entails being a free 
software license) for software (this excludes the CC BY-SA family)?

I have checked some popular free software licenses like the Mozilla 
Public License 2.0, however, this license allows proprietary-licensed 
derived works, and therefore it is not a strong Copyleft license.

All other free software licenses I have checked so far are either 
permissive or have *weak* Copyleft.

By strong Copyleft I mean a free software license that requires 
"derivate works" (as determined by Copyright law) to be free software 
(as in freedom), including works that are derivatives by making use of 
the Copylefted work through an API.

Thanks in advance.