Google Code Search lets you search for source code files by licence type, so of course I was interested in whether this could be used for quantifying indexable source code on the web. And luckily GCS lets you search for all works with a given licence. (If you don't understand why that's a big deal, try doing a search for all Creative Commons licensed work using Google Search.) Even better, using the regex facility you can search for all works! You sure as heck can't do that with a regular Google web search.

Okay, so here's the latest results, including hyperlinks to searches for you to try them yourself:

• all (by regex: .*) : 36,700,000
• gpl : 8,960,000
• lgpl : 4,640,000
• bsd : 3,110,000
• mit : 903,000
• cpl : 136,000
• artistic : 192
• apache : 156
• disclaimer : 130
• python : 108
• zope : 103
• mozilla : 94
• qpl : 86
• ibm : 67
• sleepycat : 51
• apple : 47
• lucent : 19
• nasa : 15
• alladin : 9

And here's a spreadsheet with graph included: However, note the discontinuity (in absolute and trend terms) between approximate and specific results in that (logarithmic) graph, which suggests Google's approximations are not very good.

Labels: ben, free software, licensing, quantification, search