User's Manual

MostGNUsoftware,includingsomelibraries,iscoveredbytheordinaryGNUGeneral
PublicLicense.Thislicense,theGNULesserGeneralPublicLicense,appliestocertain
designatedlibraries,andisquitedifferentfromtheordinaryGeneralPublicLicense.We
usethislicenseforcertainlibrariesinordertopermitlinkingthoselibrariesintonon‐free
programs.
Whenaprogramislinkedwithalibrary,whetherstaticallyorusingasharedlibrary,the
combinationofthetwoislegallyspeakingacombinedwork,aderivativeoftheoriginal
library.TheordinaryGeneralPublicLicensethereforepermitssuchlinkingonlyifthe
entirecombinationfitsitscriteriaoffreedom.TheLesserGeneralPublicLicensepermits
morelaxcriteriaforlinkingothercodewiththelibrary.
Wecallthislicensethe"Lesser"GeneralPublicLicensebecauseitdoesLesstoprotectthe
user'sfreedomthantheordinaryGeneralPublicLicense.Italsoprovidesotherfree
softwaredevelopersLessofanadvantageovercompetingnon‐freeprograms.These
disadvantagesarethereasonweusetheordinaryGeneralPublicLicenseformanylibraries.
However,theLesserlicenseprovidesadvantagesincertainspecialcircumstances.
Forexample,onrareoccasions,theremaybeaspecialneedtoencouragethewidest
possibleuseofacertainlibrary,sothatitbecomesade‐factostandard.Toachievethis,
non‐freeprogramsmustbeallowedtousethelibrary.Amorefrequentcaseisthatafree
librarydoesthesamejobaswidelyusednon‐freelibraries.Inthiscase,thereislittleto
gainbylimitingthefreelibrarytofreesoftwareonly,soweusetheLesserGeneralPublic
License.
Inothercases,permissiontouseaparticularlibraryinnon‐freeprogramsenablesa
greaternumberofpeopletousealargebodyoffreesoftware.Forexample,permissionto
usetheGNUCLibraryinnon‐freeprogramsenablesmanymorepeopletousethewhole
GNUoperatingsystem,aswellasitsvariant,theGNU/Linuxoperatingsystem.
AlthoughtheLesserGeneralPublicLicenseisLessprotectiveoftheusers'freedom,itdoes
ensurethattheuserofaprogramthatislinkedwiththeLibraryhasthefreedomandthe
wherewithaltorunthatprogramusingamodifiedversionoftheLibrary.
Theprecisetermsandconditionsforcopying,distributionandmodificationfollow.Pay
closeattentiontothedifferencebetweena"workbasedonthelibrary"anda"workthat