Adding "LICENSE" file

[retostauffer]

Good evening @freezenik and @zeileis

referring to issue #33 : shall might add a LICENSE file to our git repository for those not checking the DESCRIPTION file. The best suggestion I found is to add both licenses with a short header that this software is double-licensed (see merge request), though I have little experience wit this so far. @zeileis what would be your approach?

In addition to the DESCRIPTION file and (potentially) the LICENSE file one can add licenses to a github project (not sure if we nee/want this either).

[zeileis]

For now I would just put a GPL-3 file into the Git repository. This is what most users will know/expect. And those who want to use the GPL-2 license can still do so - based on the DESCRIPTION file.

And when the package has been released on CRAN, both licenses will be nicely listed/linked as well. (At that point we could also remove the Git license file again.)

[retostauffer]

@zeileis thanks, I have removed GPL-2 and the header from the LICENSE file.