Here's the actual PHP code, weighing in at 18Mb. It's probably the best way to get a feel for what it was, and it might help you decide what to do.

It includes:

• most of the site code - This code is from about a month before I moved onto a more rewarding project, but it's the last full set I have.
• automatic stylesheets/icons for iPhone and Android (not an application, but did create an icon on the home screen)
• a bunch of draft banner ads - the animated GIFs summarize how the site worked
• a research folder with information on SRS publications
• screenshots of other SRS engines

* This version may not have the correct repetition calculation. Due to the inherent time factor, it was a hassle to test, so I didn't fix that part of the code until later. *

It was admittedly an ugly (but fast loading) site. After a few weeks of cheap banner ads and seeing the minimal reuse, I just set it to coast until the year ran out.

I did do some A/B testing with email notifications about a month in. It didn't have a measurable effect of return use.

Monetization was via banner ads. Via A/B testing, the best location for the ad was under the card's question. Once flipping the card, the ad was hidden. I also deactivated the ads for awhile too see if they were too intrusive; return visitors didn't improve.

I also incorporated graphics and audio, since the most successful SRS systems seem to revolve around vocabulary. I personally used it to help learn basic Mandarin for use with my in-laws... but it is a boring way of learning a language. While it is much more effective than Rosetta Stone, it is very difficult to stay engaged.

"Remember what you read" If you take a look at a newer version of SuperMemo, it has this feature.