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The company Gluu (also at @GluuFederation) hosts the OXAuth open-source project, to which it has contributed an UMA component. The main use case for this implementation is enterprise usage. See the Enterprise UMA case study and Gluu's new special UMA page for more info. also see this YouTube video explaining how the implementation works in a developer-friendly way.
SMART project
This Java implementation includes an UMA/j framework and sample applications. See the SMART blog. The OAuth portion, originally named leeloo, has been contributed to Apache Amber (now Apache Oltu, which is going to include OpenID Connect and good JWT support too). Part the SMART project involves development of set of open-source Python libraries, called Puma, for UMA-enabling web apps to become UMA resource servers and clients. The SMARTAM.net authorization server is a running AS that third-party resource servers and clients can interact with if they wish.
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