I've often wondered ... after conversion to JPEG, is the original h.264 file still available for edit?
Is it worth editing (rendering?) in separate codecs?

I would be extremely wary of submitting to many "off-brand" sites like this. They seem to some and go, or rather appear and remain and seldom generate consistent sales. The ROI for all your work and effort produces very very little. Maybe some others can weigh in here about the quality of this site. I don't know about this site or it's history and this is the first time I have heard of it. From it's website, it looks pretty generic. If you would like a more detailed breakdown of sites by income produced - for video sales - you can take a look at my website at www.StockVideoSeller.com and/or follow the links on the resources page to other breakdowns of all the major sites.

I'm open for now income opportunities.

Me too and I wish there were more viable players. But I don't see them and I honestly think you'll find most of the little guys a major waste of time, money and effort. I expected a lot from ClipCanvas, ClipDealer, Mediastock, Stockfuel, PixelFlow, Fotolia (and who else?). Uploaded my entire portfolio to all of them. Spend days loading in the metadata. Little return for all the effort. But best of luck!