Estimating source-to-product costs for OSS: an experiment

One of my recurring themes in this blog is related to the advantages that OSS brings to the creation of new products; that is, the reduction in R&D costs through code reuse (some of my older posts: on reasons for company contribution, Why use OSS in product development, Estimating savings from OSS code reuse, or: where does the money comes from?, Another data point on OSS efficiency). I already mentioned the study by Erkko Anttila, “Open Source Software and Impact on Competitiveness: Case Study” from Helsinki University of Technology, where the author analysed the degree of reuse done by Nokia in the Maemo platform and by Apple in OSX. I have done a little experiment on my own, by asking IGEL (to which I would like to express my thanks for the courtesy and help) for the source code of their thin client line, and through inspecting the source code of the published Palm source code (available here). Of course it is not possible to inspect the code for the proprietary parts of both platforms; but through some unscientific drill-down in the binaries for IGEL, and some back of the envelope calculation for Palm I believe that the proprietary parts are less than 10% in both cases (for IGEL, less than 5% – there is a higher uncertainty for Palm).

The actual results are:

  • Total published source code (without modifications) for IGEL: 1.9GB in 181 packages; total amount of patch code: 51MB in 167 files (the remaining files are not modified). Average patch size: 305KB, Patch percentage on total publisheed code:  2.68%
  • Total published source code (without modifications) for Palm: 1.2GB in 106 packages; total amount of patch code: 55MB in 83 files (the remaining files are not modified). Average patch size: 664KB, Patch percentage on total published code: 4.58%

If we add the proprietary parts and the code modified we end up in the same approximate range found in the Maemo study, that is around 10% to 15% of code that is either proprietary or modified OSS directly developed by the company. IGEL reused more than 50 million lines of code, modified or developed around 1.3 million lines of code. Without OSS, that would have costed more than 2B$, required a full staffing of more than 700 people for an effort duration of more than 20 years. Through OSS, the estimated cost (using the more appropriate semidetached model) is around 90M$, with an average staffing of 150 people and an estimated project duration of 5 years. Palm has a similar cost (the amount of modified code is quite similar), but starting from a smaller amount of reused code (to recode everything would still require 12B$, 570 people and 18 years of work). We have to add some additional costs (for an explanation you can check my previous post on the proper use of COCOMO II and OSS, using the model by Abts, Boehm and Bailey) that would bring the total cost to a little less than 100M$ (still substantially less than the full cost of development from scratch).

Open Source allows to create a derived product (in both case of substantial complexity) reducing the cost of development to 1/20, the time to market to 1/4, the total staff necessary to more than 1/4, and in general reduce the cost of maintaining the product after delivery. I believe that it would be difficult, for anyone producing software today, to ignore this kind of results.

Addendum: I received some requests for specific parts of source code from people willing to check the kind of modifications performed. For Palm, the website provides both original source code and patches. For IGEL, I requested the access to the source code, and was kindly provided with a username and password to download it. Since the single most requested file seems to be the modified rdesktop, I have linked the GPL sources here.

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