Not currently, but in the near future I wish to adapt a small RBSD
library as a part of a larger project. I would prefer to release my
changes under the GPL.
Sounds good :).
Why GNU don't mix licences in the same file?,
Is some another problem for not do so?
There is no particular problem. It's just a general principle (for
simplicity), not a hard and fast rule.
Best,
Karl
