The LDA does not permit modification of the tax code definition to exclude such expenditures when reporting lobbying expenses.

From around 1985 the source code was widely distributed under a license that permitted sharing and modification but not commercial use.

It does not permit redistribution or modification, and thus is not considered open source or free software.

Licenses which only permit non-commercial redistribution or modification of the source code for personal use only are generally not considered as open-source licenses.

All images are licensed by the contributors using the Creative Commons cc-by-sa 2.0 licence which permits modification and redistribution of the images under certain conditions.

The licensing permits non-commercial modification and distribution of the source code, as long as all distributions include the original license, or one encompassing the original terms.

This permits use, study, and modification without restriction.

Released under a licence which permits free distribution but not modification, the Luxi fonts are not free software.

It permits free copying, modification, and redistribution with the same freedom.

Since the game code was published under a license permitting noncommercial distribution and modification, community members have created many modified versions, or mods, of the original game.