What's the difference between OSL and LGPL?

[Remco]

Someone wants to release a project under the GPL, but he can't because
the project uses Qt and CUDA. CUDA is a proprietary library, so
release under plain GPL would be impossible. However, GPL with a
special exception for CUDA would be possible. But the license of Qt
does not allow such an exception. Qt does however allow a few other
licenses as exceptions, such as the OSL and LGPL. Both could be used
for the project instead of the GPL.

Now, what's the difference between OSL and LGPL? Both allow code that
is linked to have another license. And both require the release of
source code under the same license for the code that is on "this side"
of the link. Both require a patent grant from authors.

So what's the use of the OSL? LGPL is a more popular license, so the
OSL would have to do something fundamentally different for it to be
used. Otherwise there would be license proliferation.

Remco