The Open Source Definition is the community gold standard for
licenses. The OSD is not a license itself; rather, it defines a
minimum set of rights that a license must guarantee in order to be
considered an open-source license. The OSD, and supporting materials,
may be found at the web site of the Open Source Initiative.
The widely-known OSD-conformant licenses have well-established
interpretive traditions. Developers (and, to the extent they care, users)
know what they imply, and have a reasonable take on the risks and tradeoffs
they involve. Therefore, use one of the standard licenses carried on the
OSI site if at all possible.
If you must write your own license, be sure to have it certified
by OSI. This will avoid a lot of argument and overhead. Unless
you've been through it, you have no idea how nasty a licensing
flamewar can get; people become passionate because the licenses are
regarded as almost-sacred covenants touching the core values of the
open-source community.
Furthermore, the presence of an established interpretive tradition may
prove important if your license is ever tested in court. At time of
writing (early 2002) there is no case law either supporting or invalidating
any open-source license. However, it is a legal doctrine (at least in
the U.S., and probably in other common-law countries such as England
and the rest of the British Commonwealth) that courts are supposed to
interpret licenses and contracts according to the expectations and
practices of the community in which they originated.
Take our 
