Thanks for your inquiry on agile multiple seller/vendor modules.
1. Is it possible to integrate an affiliate system, like ShareASale?
If it is PrestaShop standard module, then yes, it should be able to install together for store owner use purpose.
But there might be or might not be common code override conflicts between modules, if that is a scenario, need to merge the code for integration.
2. Is code open-source? Can it be edited by an in-house developer? What language/technology is the software built with?
All common override class code are in open code.
All css files and javascript files are in open code.
Some core PHP code of the module is obfuscated for anti-piracy purpose. But we will provide related files in open code for your customization purpose if you need to make changes by your developers.
3. Can payments go directly to Vendors and then I bill them a % commission for all sales?
Yes, you need to configure the module to "Seller Collects Payment" mode. But for this mode, all payment modules have to be integrated into our modules. We have a few this kind of modules are ready for this purpose, for example: Agile paypal Parellel/Agile Bank Wire/Agile Pay By Cheque.
If you use Agile Paypal Parallel module, owner and sellers can split the payment form customer instantly (handled by paypal) right after customer payment is done.
4. Do a lot of marketplaces currently use your software? Are you able to provide any live examples? Is the software currently maintained and updated?
You can find some showcases here - Please make sure to filter out by Agile Multiple Seller module.
5. Can commission be customized for each vendor separately? IE one vendor pays 5% commission, another 6%?
Yes, you can set a default rate that applies to all sellers.
You can also seller for each seller at different rate.
6. Is there a coupon module? What kind of coupons are supported (Sitewide / Product-Specific / Vendor-Specific)?
Currently we only support site-wide coupons, issued by store(site) owner, and use for all sellers.
But Prestashop original coupon configuration is very flexible, that you can limit a coupon to a specific product(s), categories or customers.
7. Can vendor upload/manage product list view CSV or other file upload? Similar to how powersellers manage product lists at eBay.
Yes, vendor can use CSV file to upload products(that is extension of PrestaShop original feature).
That is only available in back office, currently it is not available at front store Seller Manage Panel.