Unfortunately, the 2 GB per-file limit is not arbitrary. We discovered some years ago that downloads barely larger than 2 GB were running into mysterious problems, and ultimately our sysadmin concluded those problems were in fact due to a server-side hard limit imposed by the maximum value a 32-bit signed integer can represent: 2,147,483,647, which in bytes is 2 GiB (2.147 GB). Thus, bypassing this limit would require a major, comprehensive overhaul of our system from 32-bit to 64-bit architecture.
Although downloads are ultimately served from our S3 provisions whenever possible, the file must initially be cached in our local system before we can sync a copy of it to S3, and the earliest downloads would be served from our local system before that sync is completed; moreover, the local copy would be served as a fallback measure in case of any issues with S3 itself or with the network routing between S3 and our Tucson datacenter.
One approach you might consider is breaking up a larger file into chunks of 2 GB or less, setting up each chunk as a separate Single File Download product, then setting up the product you actually sell with "Package files from other products" to have it bundle links from the single-chunk products.
Also bear in mind how long it would take to download files that large, considering that outside of major metro areas, broadband service may top out at only 1.5 Mbps or so:
Sellers with extremely large files to provide often use a disc-fulfillment service that can automatically duplicate and mail out data DVDs on-demand whenever an order comes in, rather than expecting buyers to babysit a download potentially for hours -- this help page lists the disc fulfillment services known to integrate with E-junkie:
Finally, if you still prefer to provide your product data as a download and don't wish to use our bundling feature for that, we can recommend using us with the Continuata advanced download management service, which can support far larger files than we can, along with advanced features such as multi-part concurrent downloads that automatically reassemble into a single file upon completion, easy pausing/resuming of downloads in progress, and more. Integrating them with E-junkie is a simple matter of configuring your product with the "Send transaction data to a URL" option enabled, so you can paste the Payment Variable Information URL provided by Continuata into that product's settings, so we can notify them when the product is purchased. Find out more about Continuata here (see Products > Connect Downloader in particular):