Declaring software open-source considered helpful

There have been two Humble Bundles released in the last six months:

1. Humble Indie Bundle in December, 2010
2. Humble Frozenbyte Bundle in April, 2011

The summary statistics themselves are enough to challenge some established stereotypes, e.g. the average amount contributed by Linux users has consistently been significantly larger than the Mac OS or Windows counterparts, showing that Linux users are willing to pay more than non-linux users for quality software.

On a larger scale, considering these to be real-world economic experiments, there is still much information buried deeper in the data than can be gleaned by looking at the summary. Here, I look at five-minute sampled data to see what effect making the software open-source had on the sales:

Contribution and purchases data for the Humble Frozenbyte bundle.
The projections show what the contributions and purchases might have been if Frozenbyte had not declared their games open source.

Humble Bundles are packages of (generally cross-platform) games which are sold for a short period (a couple of weeks) being sold using the pay-what-you-want model, with the exception that one has to pay at least 1 cent to purchase them. There have been a few examples of this model put in practice, but Humble Bundles have been able to execute it with great success.

I asked Jeffry multiple times for the data, but I guess he does not want to release it to preserve anonymity (?) maybe. This data was collected from 13th April, 2011, 11 PM (CET) onwards, and was sampled at 5 minute intervals by scrapping the www.humblebundle.com page. About half the sales had already happened on the first day  of release, 12th April (the graph starts at $446,894.30 and 86,739 purchases). The left side of the graph shows the cumulative number of purchases and contribution and the right side shows the per-five-minute behavior. 

The point of interest is April 22, about 11 PM, when Frozenbyte declared that the source code for the games Shadowgrounds and Shadowgrounds: Warrior will be released. This news spread quickly. The consequences of this, as is apparent from the graph, were:

1. Though there were some high contributions (make mostly by @notch and @garrynewman, in an epic battle on the Leaderboard), only after the declaration was the high contribution rate sustained and corresponded to a high purchase rate instead of one single big purchase.
2. The total number of purchases increased by about 20,000 (using the projections)
3. The total amount earned increased by about $ 120,000 (using the projections)

In short:

Declaring your software open source will earn you more than $120,000 in the next 4 days*.

* Terms and conditions apply.