Hi,
We took a decision to remove it because we weren't aware anyone was using it - certainly none of our hosted/supported customers were using it.
It was very basic functionality that we felt over-sold the definition of e-commerce. It just renamed some things on the collection bar and added PayPal integration for payment. A better approach might be for an e-commerce system to integrate with ResourceSpace via the API, then you'd get full e-commerce capability with ResourceSpace handling your digital assets at the back end.
Where we feel functionality is not used, and isn't core to what ResourceSpace is meant to be (a DAM) we will remove it, to ensure the code base is lean and easier to support.
As a potential route you could pay a third party PHP developer to move the removed functionality into a plugin - this would mean you are still running 100% pure base code and can continue to upgrade, while also retaining e-commerce functionality. I think it wouldn't be difficult to port the e-commerce functionality into a plugin, in fact I think it would be better as a plugin.
I hope that's useful, and sorry that our decision impacted you negatively.
Dan