5
Pity indeed. I've heard that there is a Zencart module in the works, but I have no idea when it will be out.
I worked with XOSC for several months, I defended regularlly when people would complain about the lack of development, and I even tried working on it myself. I finally gave up on it due to lack of support, and security issues.
There are those who can integrate OSC into Xoops. I'd recommend
http://www.brandycoke.com/. They have been known to integrate OSC into XOOPS at least partially. Alternately, you could just edit OSC so that it resembles your XOOPS site. If you're any good at HTML/CSS [and just a little php], it can be done. Just takes some time hacking the code.
If you're looking for a [somewhat] more simple approach, my best suggestion to you would be to setup multiple single page modules [see
Xoops Documentation Site], and use the features available through PayPal to create a static storefront. The administration takes more time, but it's secure.