The 11th International Conference on Open Source Systems (OSS 2015) will celebrate a decade of advances in the use of free and open source software by emphasizing areas and topics that will drive future use over the next decade. This will be achieved through a combination of high-quality research papers, tutorials, workshops, demonstrations, and invited talks. This year OSS2015 will be co-located with the 2015 International Conference on Software Engineering (ICSE2015) as a way to cross-fertilize ideas.