What is it?
The codebase cost is an attempt to estimate how much it would cost to create a project from scratch. It is not capable of telling you what a project is “worth,” only what it would cost to produce.
How is it calculated?
We use a software costing model called COCOMO. There are several variations of this model, each with different precisions. We base our calculations on the simplest form of these models (the ‘Basic COCOMO’ model). We currently lack the information required to produce the more advanced models.
For those familiar with the details of the model, we are using coefficient values of a=2.4 and b=1.05.
You can read more in the Wikipedia entry for COCOMO.
But it seems way off!
The result of the model can seem pretty goofy in some cases. Software cost estimation is tricky business even when all the variables are known (which we certainly don’t have). One thing to remember is that COCOMO was created to model large institutional projects, which often don’t compare well with distributed open-source projects. Beyond just develoment time, COCOMO is meant to include the design, specifications drafting, reviewing, and management overhead that goes along with producing quality software.
The model seems to be most accurate with mature, large projects. Young projects with little activity are typically very overvalued.
What’s this good for?
It’s a handy tool to gauge the size of projects. People who don’t develop code don’t know whether 200,000 lines of C code is ‘a lot’ or not – so representing it in terms of money is a quick way to convey that, in this case, 200,000 lines of C is indeed ‘a lot’. It’s important to remember that the cost to produce a good software project is not necessarily a good indication of the value it has to you — so it’s important to look at other factors when evaluating projects.