4
Depending upon your needs there are several:
- Kshop (solid commerce module)
- Bookshop (commercial $$, but looks promising)
- xAsset (digital assets, very abandoned)
- Zen Cart (looks abandoned)
- xosCommerce (osCommerce integration, updated)
There is also the subscriptions module, but I don't think that's what you're looking for.
xosCommerce is in the process of being updated, but it also doesn't sound like what you need, but it's an integration of osCommerce which is the most full-featured php-based OSS commerce engine in the wild. But the learning curve is steep, too.
