some extensions are missing license-name in extension.json or $wgExtensionCredits. This means no license is specified for them in Special:Version (e.g. https://en.wikipedia.org/wiki/Special:Version) or the license is displayed as 'License' instead of 'GPL-2.0+', 'MIT' or something specific.
to fix this, we need to make changes like https://gerrit.wikimedia.org/r/#/c/264553/ in the relevant extensions. One needs to check the LICENSE or COPYING file to verify which license the extension has, and then add the license-name.
as well, some extensions are possibly missing a LICENSE or COPYING file, which would result in a broken license link.
note: the 'extensions' listed as wikibase or data values is outside scope of this task. Most of these are actually libraries and instead need to be moved to the libraries section of SpecialVersion. (see: T123937)
**Still to do:**
AbsenteeLandlord
ActiveAbstract
AddMessages
AdManager
Ads
AdvancedMeta
AJAXPoll
AkismetKlik
AllTimeZones
AnchorHandler
Annotator
ApiExplorer
ArticleFeedbackv5
ArticleIndex
ArticleRatings
Athena
AutomaticBoardWelcome
AutoProxyBlock
AWSSDK
AzharAuth
BaseHooks
BatchUserRights
BibManager
Blackout
BlameMaps
BlueSpiceCategoryManager
BlueSpiceEditNotifyConnector
BlueSpiceExtendedFilelist
BlueSpiceExtendedSearch
BlueSpiceExtensions
BlueSpiceFoundation
BlueSpiceInsertTemplate
BlueSpiceMultiUpload
BlueSpicePageAssignments
BlueSpicePageVersion
BlueSpiceSignHere
BlueSpiceSMWConnector
BoilerPlate
BookManager
BreadCrumbs2
BSSMWConnector
Calendar
Capiunto
Cards
Cargo
Carp
CategorySortHeaders
CategoryTests
CentralLogging
Challenge
ChangeAuthor
check-entry-points.py
Checkpoint
check-sync.sh
Cite
CiteThisPage
Citoid
ClientSide
CloseWikis
CodeMirror
CollaborationKit
Commentbox
CommentPages
Comments
CommonMessages
CommunityApplications
CommunityHiring
CommunityVoice
ConditionalShowSection
Configure
CongressLookup
ContentTranslation
ContributionReporting
ContributionScores
ContributionsList
ContributionTracking
Contributors
ContributorsAddon
Convert2Wiki
CopyToClipboard
CreateRedirect
CreditsSource
CSS
CustomPage
CustomUserSignup
D3Loader
DebugMode
DebugTemplates
Description2
DeviceMapLogCapture
Diagnosis
DidYouMean
DisableAccount
DiscussionThreading
DisqusTag
DjangoAnalytics
DonationInterface
DoubleWiki
DownloadCounter
DPLforum
Drafts
DumpHTML
DynamicPageList
DynamicSidebar
EditNotify
EditOwn
EditPageTracking
EditSimilar
EditUser
EmailAuth
EmailDiff
EnhanceContactForm
ErrorHandler
EtherpadLite
examples
ExtraLanguageLink
Favorites
FeedsFromPrivateWikis
FilterListUsers
FirstSteps
FixedHeaderTable
FlickrAPI
FlvHandler
ForcePreview
FormatNum
FormelApplet
FormPreloadPostCache
Foxway
FundraiserLandingPage
FundraisingChart
FundraisingEmailUnsubscribe
FundraisingTranslateWorkflow
Genderize
Genealogy
Git2Pages
GlobalContributions
GlobalUserrights
GoogleAnalyticsMetrics
GoogleAnalyticsTopPages
GoogleCustomWikiSearch
GoogleDocs4MW
GoogleDocTag
GoogleGeocode
GooglePlaces
GooglePlusOne
GoToShell
GPGMail
GroupsSidebar
HelpPages
HidePrefix
HierarchyBuilder
HighlightjsIntegration
Hreflang
HSTS
I18nTags
IframePage
IfTemplates
ImageLink
ImageRating
ImportArticles
ImportFreeImages
IndexFunction
Insider
InteractiveBlockMessage
Interlanguage
InterwikiIntegration
JSBreadCrumbs
JsonData
LandingCheck
LanguageSelector
LanguageTag
LanguageTool
LastModified
LDAPAuthorization
licencemissing
LifeWeb
LifeWebCore
LinkedWiki
LinkFilter
LinkSuggest
Listings
ListSignup
LockDownEnglishPages
LogoFunctions
LookupUser
LoopFunctions
MadLib
MagicNumberedHeadings
Mailgun
Maintenance
MarkAsHelpful
MassMessageEmail
MediaWikiChat
Memento
MessageCommons
Minifier
MiniInvite
MobileDetect
MOOC
Moodle
MoveToCommons
MoveToCommonsClient
MP3MediaHandler
Mpdf
MsCatSelect
MsInsert
MsLinks
MsWikiEditor
MultimediaPlayer
MultiUpload
MWVersionInfo
NamespaceHTML
NamespacePaths
NamespacePopups
NamespaceRelations
NaturalLanguageList
NewestPages
News
NewsBox
NewSignupPage
NewUserActions
NewUserNotif
NewUsersList
Nonlinear
normal
NotebookViewer
NukeDPL
NumberOfComments
NumberOfWikis
Numbertext
OdbcDatabase
OfflineImportLexicon
OnlineStatusBar
OOUIPlayground
OpenIDConnect
OpenStreetMapSlippyMap
OracleTextSearch
PageCreationNotif
PageDisqus
PageInCat
PageLanguage
PageNotice
PagePopups
PagesList
ParentPage
ParserMigration
Parsoid
ParsoidBatchAPI
PdfExport
PerPageLicense
PGFTikZ
PHPExcel
PhpHighlight
PhpTags
PhpTagsFunctions
PhpTagsMaps
PhpTagsSMW
PhpTagsSPARQL
PhpTagsStorage
PhpTagsWidgets
PhpTagsWiki
PictureGame
PipeEscape
PluggableAuth
Poll
PollNY
PopcornEditor
PopupPages
PostEdit
PrefSwitch
Premoderation
Prezi
PropertySuggester
PureWikiDeletion
PurgeClickThrough
PushToWatch
Quantcast
QuickSearchLookup
QuickSurveys
quick-update
QuizGame
QuizTabulate
RandomFeaturedUser
RandomGameUnit
RandomImage
RandomImageByCategory
RandomInCategory
RandomUsersWithAvatars
ReaderFeedback
ReassignEdits
RecentActivityFeed
RefreshSpecial
RegexBlock
RegexFunctions
RelatedArticles
RelatedLinks
RelatedSites
RelationLinks
RestBaseUpdateJobs
RevealEmail
RevisionCommentSupplement
RevisionSlider
RT
SacredText
SafeDelete
Sarcasm
ScanSet
SearchExtraNS
SearchStats
SecurePasswords
SecureSessions
SemanticBundle
SemanticImageAnnotator
SemanticLinks
SemanticMediaWiki
SemanticWebBrowser
Sentry
SharedCssJs
SharedHelpPages
ShortUrl
ShoutWikiAds
ShoutWikiAPI
ShowMe
SidebarDonateBox
SignWritingMediaWikiPlugin
SimpleAntiSpam
SimpleChanges
SimpleSAMLphp
SimpleSecurity
SimpleSort
SimpleSurvey
SiteMetrics
SiteScout
SkinPerNamespace
SkinPerPage
SlimboxThumbs
SmoothGallery
Snippet
SocialLogin
SocialProfile
SoftwareVersion
Solarium
SolrStore
sort-gitmodules.py
SoundManager2Button
SpamDiffTool
SpamRegex
SpecialNamespaces
SportsTeams
SSLClientAuthentication
StaffEdits
StaffPowers
StarterWiki
StatCounter
StlHandler
StopForumSpam
StringFunctionsEscaped
SubPageList3
Suhosin
SVGEdit
SwarmExport
SwiftCloudFiles
sync-with-gerrit.py
Tabber
TemplateInfo
TestLanguageNameGrammar
TextScroller
Theme
ThemeDesigner
TheWikipediaLibrary
ThumbParser
TimelineTable
TimeMachine
TimezoneSelector
Tooltip
TopLists
TranslateSvg
Transliterator
TweetANew
TwitterCards
TwnMainPage
TwoColConflict
TwoFactorAuthentication
UIFeedback
UnicodeConverter
UnitTest
UniversalLanguageSelector
UnusedRedirects
update-extensions.sh
UpdateMediaWiki
UploadBlacklist
UploadLocal
UploadLogo
UrlGetParameters
URNames
USERNAME
UserOptionStats
UserPageViewTracker
UserStatus
UserThrottle
Vector
Video
ViewFiles
Vine
VirtualKeyboard
VisualChat
VisualEditor
VoteNY
WantedPagesFromNS
WebChat
WebPlatformAuth
WebPlatformSearchAutocomplete
WhitelistPages
WhiteSpace
WhoIsWatching
Whoops
WikEdDiff
WikiArticleFeeds
WikibaseLexeme
WikibaseMediaInfo
WikiCategoryTagCloud
WikidataEntitySuggester
WikidataPageBanner
WikiLabels
WikiLexicalData
Wikilog
WikiLovesMonuments
WikimediaIncubator
WikimediaShopLink
WikiShare
Wikispeech
WikiTextLoggedInOut
WikiTwidget
WikivoteMapsYandex
WindowsAzureSDK
WindowsAzureStorage
XenForoAuth
XMLContentExtension
YetAnotherKeywords
YouTube
ZoomableImages