dc plugin source code is in public domain
The formal description is:

"
I, the copyright holder of this work, hereby release it into the
public domain. This applies worldwide.

In case this is not legally possible:
I grant anyone the right to use this work for any purpose, without
any conditions, unless such conditions are required by law.
"

This means you can do everything you want with this source code,
including relicesing under any license you want without any notice
or even using it for commercial purpose.
