There is no software on the market that is compatible with Publisher. The best thing you can do is export from a .PUB file to .DOC, but you need publisher to do this and you will lose a TON of formatting.
Scribus is probably less like Publisher, and more like PageMaker / InDesign / Quark Express.
Unfortunately there isn't an "Open Source Publisher" out there, presumably because there is far less demand these days for printed materials which are sort of going the way of the buffalo. More people are using the web to get their information out to people so I think printing just seems archaic to developers.
I use OpenOffice Draw for desktop publishing. It's not exactly what it was designed for, but it does a good job, and can export directly to PDF. I've also used Scribus and Inkscape for some things too.
I find that Scribus does better when more text is involved, and OpenOffice Draw does better when more objects are involved. I think Scribus has a steeper learning curve, likely due to the fact that it's a more professional tool and a lot of the terminology used is printing industry specific.
Cheerio,
-n8