A Semacode is a machine-readable, Data Matrix symbol which encodes URLs; basically it’s a barcode for web locations. The idea is to create one of these labels which looks like a complicated crossword puzzle, and through it you can be connected to a URL which will provide you with more information on the object that the semacode is pasted to. Currently they are being used through cellphone with cameras, and full internet capabilities, although you do need to download additional software for this. (A draw back seems to be that this technology only works with a handful of cellphone operating systems.) The idea is to be able to get more information of whatever you are looking at on the spot.
The company in Canada that created these tags says on their website that the tags can be used without restrictions, and that the software used to produce them is free of charge and available for non-commercial use. This technology is currently licensed under the GNU General Public License.
Currently one of the bigger projects using this technology is Semapedia which aims at bringing the vast content available on Wikipedia to the real world. Semapedia is a community project and anyone can create semapedia tags, print them, and begin hyperlinking objects they believe other’s might want more information about. Another project using semacodes is the eRuv. This project along Manhattan’s Third Ave attempts to use semacodes to explain the area’s history; Third Ave marks a boundary for a Hasidic community in the old Lower East Side.
Image info here.