It's the other way around, the name of the project on SF is modplug-xmms and libmodplug is what to search for in the rss feed.

Hm, so how should this be configured? The project name is libmodplug (ditto its tarball name), the SF project it is under is modplug-xmms. Can the SF backend be used for this case at all without lying about the project name at all? With cnucnu this was not a problem.

The project is modplug-xmms, it just releases several sub-project including libmodplug.

Ok, if you want to have it that way. But I need monitoring for the modplugtools and libmodplug "subprojects", they have different version numbering schemes. How do I configure them in Anitya?

I do not want to have it this way, I'm just trying to explain the way I designed it. Yes it might not be perfect, yes it can be improved and yes you are coming across as pretty harsh, for a reason I'm not sure to understand.

As for how to set it up, as it's like I said in the first comment, set modplug-xmms as project name and libmodplug as sourceforge name.
If the constraint on unique name+homepage bits you, then we are back on the issue #80 and we'll have to come up with something for this (not sure what for the moment).

I don't mean to be harsh, but from your very short comments it was impossible for me to know what is working as designed, and what is a bug, and what is the way I should configure stuff, so I have to keep guessing and asking for more information.

Before I go and make a mess (the possibilities to delete things seem to be limited at the moment so I'd rather ask), could you please confirm how do I now configure two subprojects for modplug-xmms: libmodplug and modplugtools. Do I configure two different projects by the modplug-xmms name in Anitya and set sourceforge name for one of them to libmodplug and modplugtools for the other?

I think you are in the same situation as #80, 1 project releasing multiples sources and that seems not to work as I thought and there is likely a bug or something broken in the design.
I'll look closer into this as I thought I did encounter this situation when writing anitya.

Let me get back to you with the proper setup or a fix :-)

Ok I tried to summarize a little the situation and problem here: http://blog.pingoured.fr/index.php?post/2015/02/25/About-SourceForge-and-anitya

#80 is indeed the same thing, better to continue discussion there.