ArsDigita published in 2001 the ArsDigita Public License (ADPL), which covers ACS Classic starting with v4.6. The OpenACS gatekeepers strongly request that all OpenACS software contributors abstain from downloading or viewing ADPL-covered source code.

The OpenACS gatekeepers have read the ADPL and have concluded that code released under this license is clearly incompatible with the GPL, the license under which OpenACS is distributed. The OpenACS project wishes to strictly abide by all third-party code licenses. The gatekeepers have decided to exclude any trace of ADPL-licensed code in OpenACS in order to maximally comply with the ADPL and ensure that the OpenACS remains freely distributed under the GPL. This generally applies to all non-GPL-compatible code, but is particularly important in this case, where the functional goals of OpenACS and ACS are similar.

Because the extent of such a license's power is uncertain, the OpenACS project cannot even take the risk of viewing ADPL-licensed source code.

If you'd like to find out more, check out:

• our quick primer on Open-Source Licensing,
• the FSF's License List,
• the FSF's Categories of Software,
• OSI's Open-Source Definition.