I'm just thinking about to make a Rosetta++ Ebuild available. However, the Rosetta++ sources are license-fee free only for academic and non-profit use, so everyone who would like to run Rosetta++ locally, must first register at http://www.rosettacommons.org/software/index.html, and would then get a username, a password and a download link for the sources via email.
As far as I see, the Gentoo ebuild system does not yet handle this situation,
whereas providing access to source codes that way is not uncommom.
Steps to Reproduce:
There is a way. Use RESTRICT="fetch" and pkg_nofetch to instruct the user what to do. See sci-chemistry/cns as an example.
RESTRICT=fetch does that already. The way to do it is to place the downloaded resources in $DISTDIR yourself and then run emerge.
(In reply to comment #3)
I think, using pkg_nofetch() is ok for now, thank you very much for that hint. However, a simple portage module managing licenses similar to kde's kwallet daemon could provide a general solution.
If you are using RESTRICT="fetch" to deal with license restriction imposed by packets like rosetta++, which in turn need sources from elsewhere to build certain optional features, then you are out of luck, because the active fetch restriction will prevent you from fetching any other sources you need, even though they would be freely available.
In this example, as rosetta++ optionally uses some internal API from boinc, boinc sources were needed. As luckily boinc already exists as a gentoo package, I just had to put into DEPEND, and then accessed the associated source archive via DISTDIR within pkg_setup().
But this is neither a clean solution, nor is it always applicable. At least there should be a possibility to query an ebuild for it's source archive name, as a shell function similar to best_version() or as an extension of portageq.
Sorry, but this is not even a supported package due to the very same fact that there is no ebuild for it. Please develop that ebuild elsehwere - this bug tracker is not the appropriate place.