The GPS Dancer software is available under the Apache 2.0 open source license, with some limitations.

The following elements of the operational Dancer software are not public:

  • The part of the software that controls the run-time version, so that all on-line processes run exactly the same code
  • The part of the software that deals with starting up a network on the public internet
  • Some details of the connection protocol between any two GPS Dancer peers

If these details would be published the on-line system would no longer be secure: malicious software could connect to Dancer peers either to access its data, or to interfere with the proper solution process.

For all mathematical models, data processing steps, file interfaces and other parts of the analysis software, the Apache 2.0 license applies. This means that you may use the software in any way you like as long as you provide proper credit to the creators. It also means that the software is provided "as is", without any warranty and without accepting any liability.

There has been some discussion on the actual license, and three options were compared:

  • A native (Dancer-invented) license - this would have required some careful interaction with lawyers and interested parties, which was neither feasible for a voluntary project, nor necessary: usable licenses exist for similar projects, and the advantage of using an existing license is that most users will already be familiar with them. 
  • The GNU Public License. This license has the nasty property of enforcing the same conditions on any derived work or partly reused software, which ends up being counter-productive.
  • The Apache II license - the conditions of this license are very similar to GNU, but without some restrictive aspects. In fact, Apache does not even insist on publishing the source code, although a JAVA process will be easy to uncompile anyway.

The Apache II license seems to best match the spirit of the Dancer project, and does not interfere with the capability to maintain in control of some parts of the run-time system, such as the facilities for automatic software updates.

So - Apache it is.


Project details

Ultimate Browsers SupportThe GPS Dancer project started in 2007 as a voluntary project of a working group of the International Association of Geodesy.

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Square dance algorithm

Great Docs and SupportThe GPS Dancer system was named after its "square dance" exchange algorithm. Of course, it also wants to to make the GPS reference frame denser.


Here, there be pirates

The Dancer on-line network became immune against internet connection problems by leaving the US marines, and becoming a pirate.

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