The problem is, if a piece of software is under the Apache (or similar)
license, it is perfectly legal to fork it under a proprietary license.
Changes can be made, that are secret and there is no obligation to publish
the software under a free software license.
This means, the new proprietary version may be incompatible with the old
version, pack new features and be proprietary. A good scenario for confusing
people and forcing them to switch to a proprietary program.
Licenses like the Apache or BSD licenses allow this. It basically is a
disadvantage for the developers, since they will not get any source code of
the improved proprietary version in case something like that happens. But
some people just enjoy knowing that their work is good enough so that big
companies find it appealing to adopt it.
I'd rather call that stealing software than the definition of software theft
we are fed nowadays.
