1. Are Apsona still alive and supporting this product?
I emailed them yesterday but have received no replies.
Yes, I think so...but they are always very busy with paying customers.

2. Can anyone explain their business model? How do they make money with free service and free support?
Custom work, I think.

3. Can I import/alter product attributes with SA? (ie the tables: products_attributes, products_options_values and products_options)
I price all of my products via Catalog -> Attributes Controller.
Yes - although I don't use it for that.

4. Can anyone tell me how much of my shop data would be passed through Apsona's server? I see that they effectively control the service but, as my shop is confidential (sales, finances, and especially customer data), I would need to know what data gets sent where and what control I have over that.
http://www.zen-cart.com/showthread.p...053#post878053

None is sent to their servers. The code is downloaded from their site each time you start it up and that's it.

I've been using it for ages and if one day they start to charge, I'll still use it. It works.