Users Guide

Fi nal l y, sof t war e pat ent s pose a const ant t hr eat t o t he exi st ence of any f r ee pr ogr am. We wi sh t o make sur e
t hat a company cannot ef f ect i vel y r est r i ct t he user s of a f r ee pr ogr am by obt ai ni ng a r est r i ct i ve l i cense
f r om a pat ent hol der . Ther ef or e, we i nsi st t hat any pat ent l i cense obt ai ned f or a ver si on of t he l i br ar y must
be consi st ent wi t h t he f ul l f r eedom of use speci f i ed i n t hi s l i cense.
Most GNU sof t war e, i ncl udi ng some l i br ar i es, i s cover ed by t he or di nar y GNU Gener al Publ i c Li cense. Thi s
l i cense, t he GNU Lesser Gener al Publ i c Li cense, appl i es t o cer t ai n desi gnat ed l i br ar i es, and i s qui t e
di f f er ent f r om t he or di nar y Gener al Publ i c Li cense. We use t hi s l i cense f or cer t ai n l i br ar i es i n or der t o
per mi t l i nki ng t hose l i br ar i es i nt o non- f ree pr ogr ams.
When a pr ogr am i s l i nked wi t h a l i br ar y, whet her st at i cal l y or usi ng a shar ed l i br ar y, t he combi nat i on of t he
t wo i s l egal l y speaki ng a combi ned wor k, a der i vat i ve of t he or i gi nal l i br ar y. The or di nar y Gener al Publ i c
Li cense t her ef or e per mi t s such l i nki ng onl y i f t he ent i r e combi nat i on f i t s i t s cr i t er i a of f r eedom. The
Lesser Gener al Publ i c Li cense per mi t s mor e l ax cr i t er i a f or l i nki ng ot her code wi t h t he l i br ar y.
We cal l t hi s l i cense t he "Lesser " Gener al Publ i c Li cense because i t does Less t o pr ot ect t he user ' s f r eedom
t han t he or di nar y Gener al Publ i c Li cense. I t al so pr ovi des ot her f r ee sof t war e devel oper s Less of an
advant age over compet i ng non- f r ee pr ogr ams. These di sadvant ages ar e t he r eason we use t he or di nar y Gener al
Publ i c Li cense f or many l i br ar i es. However , t he Lesser l i cense pr ovi des advant ages i n cer t ai n speci al
ci r cumst ances.
For exampl e, on r ar e occasi ons, t her e may be a speci al need t o encour age t he wi dest possi bl e use of a cer t ai n
l i br ar y, so t hat i t becomes a de- f act o st andar d. To achi eve t hi s, non- f ree pr ogr ams must be al l owed t o use
t he l i br ar y. A mor e f r equent case i s t hat a f r ee l i br ar y does t he same j ob as wi del y used non- f r ee l i br ar i es.
I n t hi s case, t her e i s l i t t l e t o gai n by l i mi t i ng t he f r ee l i br ar y t o f r ee sof t war e onl y, so we use t he
Lesser Gener al Publ i c Li cense.
I n ot her cases, per mi ssi on t o use a par t i cul ar l i br ar y i n non- f r ee pr ogr ams enabl es a gr eat er number of
peopl e t o use a l ar ge body of f r ee sof t war e. For exampl e, per mi ssi on t o use t he GNU C Li br ar y i n non- f r ee
pr ogr ams enabl es many mor e peopl e t o use t he whol e GNU oper at i ng syst em, as wel l as i t s var i ant , t he
GNU/ Li nux oper at i ng syst em.
Al t hough t he Lesser Gener al Publ i c Li cense i s Less pr ot ect i ve of t he user s' f r eedom, i t does ensur e t hat t he
user of a pr ogr am t hat i s l i nked wi t h t he Li br ar y has t he f r eedom and t he wher ewi t hal t o r un t hat pr ogr am
usi ng a modi f i ed ver si on of t he Li br ar y.
The pr eci se t er ms and condi t i ons f or copyi ng, di st r i but i on and modi f i cat i on f ol l ow. Pay cl ose at t ent i on t o
t he di f f er ence bet ween a "wor k based on t he l i br ar y" and a " wor k t hat uses t he l i br ar y". The f or mer cont ai ns
code der i ved f r om t he l i br ar y, wher eas t he l at t er must be combi ned wi t h t he l i br ar y i n or der t o r un.
GNU LESSER GENERAL PUBLI C LI CENSE
TERMS AND CONDI TI ONS FOR COPYI NG, DI STRI BUTI ON AND MODI FI CATI ON
0. Thi s Li cense Agr eement appl i es t o any sof t war e l i br ar y or ot her pr ogr am whi ch cont ai ns a not i ce pl aced by
t he copyr i ght hol der or ot her aut hor i zed par t y sayi ng i t may be di st r i but ed under t he t er ms of t hi s Lesser
Gener al Publ i c Li cense ( al so cal l ed "t hi s Li cense") . Each l i censee i s addr essed as "you" .
A "l i br ar y" means a col l ect i on of sof t war e f unct i ons and/ or dat a pr epar ed so as t o be conveni ent l y l i nked
wi t h appl i cat i on pr ogr ams ( whi ch use some of t hose f unct i ons and dat a) t o f or m execut abl es.
The "Li br ar y", bel ow, r ef er s t o any such sof t war e l i br ar y or wor k whi ch has been di st r i but ed under t hese
t er ms. A "wor k based on t he Li br ar y" means ei t her t he Li br ar y or any der i vat i ve wor k under copyr i ght l aw:
t hat i s t o say, a wor k cont ai ni ng t he Li br ar y or a por t i on of i t , ei t her ver bat i m or wi t h modi f i cat i ons
and/ or t r ansl at ed st r ai ght f or war dl y i nt o anot her l anguage. ( Her ei naf t er , t ransl at i on i s i ncl uded wi t hout
l i mi t at i on i n t he t er m " modi f i cat i on" . )
"Sour ce code" f or a wor k means t he pr ef er red f or m of t he wor k f or maki ng modi f i cat i ons t o i t . For a l i br ar y,
compl et e sour ce code means al l t he sour ce code f or al l modul es i t cont ai ns, pl us any associ at ed i nt er f ace