Right LICENSE* values for a GPLv2 port with a licensing exception

[Raphael Kubo da Costa]

Hello there,

I'm currently working on porting xsd [1], which is a GPLv2-licensed with
an exception that allows the distribution of derivative works under
other free software licenses.  The contents of this exception can be
found in [2].

In this case, how am I supposed to set the LICENSE* variables in the
Makefile?  Should I use LICENSE_COMB=dual and consider FLOSSE a separate
license that must be agreed to besides the GPLv2?

[1] http://www.codesynthesis.com/projects/xsd/
[2] http://www.codesynthesis.com/projects/xsd/FLOSSE